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 $113.95   3.725%   $118.1946   $118.19   $118.20   $118.20  
  Purchase #2 $233.76   7.557%   $251.4252   $251.43   $251.45   $251.40  
  Purchase #3 $166.92   4.109%   $173.7787   $173.78   $173.80   $173.80  
  Purchase #4 $178.54   9.319%   $195.1781   $195.18   $195.20   $195.20  
  Purchase #5 $87.56   6.616%   $93.353   $93.35   $93.35   $93.40  
  Purchase #6 $133.77   3.126%   $137.9517   $137.95   $137.95   $138.00  
  Purchase #7 $73.28   13.853%   $83.4315   $83.43   $83.45   $83.40  
  7 purchase totals = $987.78       $1,053.3128   $1,053.31   $1,053.40   $1,053.40