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 $58.66   5.675%   $61.989   $61.99   $62.00   $62.00  
  Purchase #2 $13.81   7.264%   $14.8132   $14.81   $14.80   $14.80  
  Purchase #3 $152.63   6.256%   $162.1785   $162.18   $162.20   $162.20  
  Purchase #4 $83.71   12.232%   $93.9494   $93.95   $93.95   $93.90  
  Purchase #5 $242.66   8.521%   $263.3371   $263.34   $263.35   $263.30  
  Purchase #6 $33.79   8.610%   $36.6993   $36.70   $36.70   $36.70  
  Purchase #7 $19.37   12.447%   $21.781   $21.78   $21.80   $21.80  
  7 purchase totals = $604.63       $654.7475   $654.75   $654.80   $654.70