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 $33.56   5.297%   $35.3377   $35.34   $35.35   $35.30  
  Purchase #2 $168.73   5.298%   $177.6693   $177.67   $177.65   $177.70  
  Purchase #3 $209.30   9.864%   $229.9454   $229.95   $229.95   $229.90  
  Purchase #4 $150.71   6.824%   $160.9945   $160.99   $161.00   $161.00  
  Purchase #5 $216.31   9.424%   $236.6951   $236.70   $236.70   $236.70  
  Purchase #6 $233.37   11.807%   $260.924   $260.92   $260.90   $260.90  
  Purchase #7 $87.98   3.674%   $91.2124   $91.21   $91.20   $91.20  
  7 purchase totals = $1,099.96       $1,192.7784   $1,192.78   $1,192.75   $1,192.70