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 $90.29   5.161%   $94.9499   $94.95   $94.95   $94.90  
  Purchase #2 $210.48   3.696%   $218.2593   $218.26   $218.25   $218.30  
  Purchase #3 $24.79   5.485%   $26.1497   $26.15   $26.15   $26.10  
  Purchase #4 $201.45   4.218%   $209.9472   $209.95   $209.95   $209.90  
  Purchase #5 $64.33   5.255%   $67.7105   $67.71   $67.70   $67.70  
  Purchase #6 $168.95   13.482%   $191.7278   $191.73   $191.75   $191.70  
  Purchase #7 $9.34   9.502%   $10.2275   $10.23   $10.25   $10.20  
  7 purchase totals = $769.63       $818.9719   $818.98   $819.00   $818.80