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 $237.49   10.676%   $262.8444   $262.84   $262.85   $262.80  
  Purchase #2 $212.78   10.453%   $235.0219   $235.02   $235.00   $235.00  
  Purchase #3 $105.62   4.340%   $110.2039   $110.20   $110.20   $110.20  
  Purchase #4 $216.67   3.673%   $224.6283   $224.63   $224.65   $224.60  
  Purchase #5 $43.63   6.312%   $46.3839   $46.38   $46.40   $46.40  
  Purchase #6 $178.71   9.247%   $195.2353   $195.24   $195.25   $195.20  
  Purchase #7 $41.44   10.588%   $45.8277   $45.83   $45.85   $45.80  
  7 purchase totals = $1,036.34       $1,120.1454   $1,120.14   $1,120.20   $1,120.00