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 $104.51   11.695%   $116.7324   $116.73   $116.75   $116.70  
  Purchase #2 $84.88   9.516%   $92.9572   $92.96   $92.95   $93.00  
  Purchase #3 $60.29   13.474%   $68.4135   $68.41   $68.40   $68.40  
  Purchase #4 $245.81   9.518%   $269.2062   $269.21   $269.20   $269.20  
  Purchase #5 $110.31   8.504%   $119.6908   $119.69   $119.70   $119.70  
  Purchase #6 $70.89   3.451%   $73.3364   $73.34   $73.35   $73.30  
  Purchase #7 $119.92   5.795%   $126.8694   $126.87   $126.85   $126.90  
  7 purchase totals = $796.61       $867.2059   $867.21   $867.20   $867.20