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 $82.89   11.420%   $92.356   $92.36   $92.35   $92.40  
  Purchase #2 $43.54   11.738%   $48.6507   $48.65   $48.65   $48.70  
  Purchase #3 $57.35   10.690%   $63.4807   $63.48   $63.50   $63.50  
  Purchase #4 $239.87   6.472%   $255.3944   $255.39   $255.40   $255.40  
  Purchase #5 $123.86   4.209%   $129.0733   $129.07   $129.05   $129.10  
  Purchase #6 $242.54   7.409%   $260.5098   $260.51   $260.50   $260.50  
  Purchase #7 $249.39   7.103%   $267.1042   $267.10   $267.10   $267.10  
  7 purchase totals = $1,039.44       $1,116.5691   $1,116.56   $1,116.55   $1,116.70