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 $61.38   12.388%   $68.9838   $68.98   $69.00   $69.00  
  Purchase #2 $218.46   8.532%   $237.099   $237.10   $237.10   $237.10  
  Purchase #3 $87.94   4.349%   $91.7645   $91.76   $91.75   $91.80  
  Purchase #4 $49.95   11.832%   $55.8601   $55.86   $55.85   $55.90  
  Purchase #5 $197.38   7.727%   $212.6316   $212.63   $212.65   $212.60  
  Purchase #6 $148.60   11.304%   $165.3977   $165.40   $165.40   $165.40  
  Purchase #7 $249.88   13.170%   $282.7892   $282.79   $282.80   $282.80  
  7 purchase totals = $1,013.59       $1,114.5259   $1,114.52   $1,114.55   $1,114.60