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 $112.69   11.794%   $125.9807   $125.98   $126.00   $126.00  
  Purchase #2 $215.97   8.766%   $234.9019   $234.90   $234.90   $234.90  
  Purchase #3 $69.58   7.251%   $74.6252   $74.63   $74.65   $74.60  
  Purchase #4 $54.30   4.794%   $56.9031   $56.90   $56.90   $56.90  
  Purchase #5 $32.64   8.765%   $35.5009   $35.50   $35.50   $35.50  
  Purchase #6 $49.41   4.438%   $51.6028   $51.60   $51.60   $51.60  
  Purchase #7 $114.39   13.751%   $130.1198   $130.12   $130.10   $130.10  
  7 purchase totals = $648.98       $709.6344   $709.63   $709.65   $709.60