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 $55.56   11.658%   $62.0372   $62.04   $62.05   $62.00  
  Purchase #2 $225.27   5.154%   $236.8804   $236.88   $236.90   $236.90  
  Purchase #3 $237.41   10.361%   $262.0081   $262.01   $262.00   $262.00  
  Purchase #4 $49.55   3.304%   $51.1871   $51.19   $51.20   $51.20  
  Purchase #5 $146.25   9.546%   $160.211   $160.21   $160.20   $160.20  
  Purchase #6 $79.84   11.174%   $88.7613   $88.76   $88.75   $88.80  
  Purchase #7 $159.42   7.525%   $171.4164   $171.42   $171.40   $171.40  
  7 purchase totals = $953.30       $1,032.5015   $1,032.51   $1,032.50   $1,032.50