Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $88.57   7.329%   $95.0613   $95.06   $95.05   $95.10  
  Purchase #2 $152.87   11.108%   $169.8508   $169.85   $169.85   $169.90  
  Purchase #3 $103.76   13.807%   $118.0861   $118.09   $118.10   $118.10  
  Purchase #4 $165.52   13.810%   $188.3783   $188.38   $188.40   $188.40  
  Purchase #5 $197.70   9.745%   $216.9659   $216.97   $216.95   $217.00  
  Purchase #6 $137.44   12.422%   $154.5128   $154.51   $154.50   $154.50  
  Purchase #7 $192.48   10.535%   $212.7578   $212.76   $212.75   $212.80  
  7 purchase totals = $1,038.34       $1,155.6130   $1,155.62   $1,155.60   $1,155.80