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 $67.26   11.792%   $75.1913   $75.19   $75.20   $75.20  
  Purchase #2 $75.50   8.110%   $81.6231   $81.62   $81.60   $81.60  
  Purchase #3 $107.84   4.425%   $112.6119   $112.61   $112.60   $112.60  
  Purchase #4 $116.57   4.340%   $121.6291   $121.63   $121.65   $121.60  
  Purchase #5 $192.54   6.443%   $204.9454   $204.95   $204.95   $204.90  
  Purchase #6 $189.84   10.540%   $209.8491   $209.85   $209.85   $209.80  
  Purchase #7 $227.35   9.660%   $249.312   $249.31   $249.30   $249.30  
  7 purchase totals = $976.90       $1,055.1619   $1,055.16   $1,055.15   $1,055.00