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 $210.70   10.129%   $232.0418   $232.04   $232.05   $232.00  
  Purchase #2 $194.33   8.424%   $210.7004   $210.70   $210.70   $210.70  
  Purchase #3 $60.48   13.820%   $68.8383   $68.84   $68.85   $68.80  
  Purchase #4 $188.68   13.266%   $213.7103   $213.71   $213.70   $213.70  
  Purchase #5 $62.90   6.493%   $66.9841   $66.98   $67.00   $67.00  
  Purchase #6 $176.37   12.595%   $198.5838   $198.58   $198.60   $198.60  
  Purchase #7 $169.33   8.124%   $183.0864   $183.09   $183.10   $183.10  
  7 purchase totals = $1,062.79       $1,173.9451   $1,173.94   $1,174.00   $1,173.90