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 $57.56   7.729%   $62.0088   $62.01   $62.00   $62.00  
  Purchase #2 $181.91   10.452%   $200.9232   $200.92   $200.90   $200.90  
  Purchase #3 $64.28   3.828%   $66.7406   $66.74   $66.75   $66.70  
  Purchase #4 $74.98   5.204%   $78.882   $78.88   $78.90   $78.90  
  Purchase #5 $209.58   13.746%   $238.3889   $238.39   $238.40   $238.40  
  Purchase #6 $216.84   13.761%   $246.6794   $246.68   $246.70   $246.70  
  Purchase #7 $232.55   11.831%   $260.063   $260.06   $260.05   $260.10  
  7 purchase totals = $1,037.70       $1,153.6859   $1,153.68   $1,153.70   $1,153.70