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 $61.67   9.669%   $67.6329   $67.63   $67.65   $67.60  
  Purchase #2 $85.95   9.715%   $94.3   $94.30   $94.30   $94.30  
  Purchase #3 $95.27   6.195%   $101.172   $101.17   $101.15   $101.20  
  Purchase #4 $54.27   10.757%   $60.1078   $60.11   $60.10   $60.10  
  Purchase #5 $124.87   7.403%   $134.1141   $134.11   $134.10   $134.10  
  Purchase #6 $140.81   3.819%   $146.1875   $146.19   $146.20   $146.20  
  Purchase #7 $121.27   7.851%   $130.7909   $130.79   $130.80   $130.80  
  7 purchase totals = $684.11       $734.3052   $734.30   $734.30   $734.30