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 $60.71   3.134%   $62.6127   $62.61   $62.60   $62.60  
  Purchase #2 $244.63   4.660%   $256.0298   $256.03   $256.05   $256.00  
  Purchase #3 $216.62   9.301%   $236.7678   $236.77   $236.75   $236.80  
  Purchase #4 $121.52   9.489%   $133.051   $133.05   $133.05   $133.10  
  Purchase #5 $167.98   13.298%   $190.318   $190.32   $190.30   $190.30  
  Purchase #6 $247.44   13.309%   $280.3718   $280.37   $280.35   $280.40  
  Purchase #7 $211.43   6.414%   $224.9911   $224.99   $225.00   $225.00  
  7 purchase totals = $1,270.33       $1,384.1422   $1,384.14   $1,384.10   $1,384.20