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 $114.27   7.511%   $122.8528   $122.85   $122.85   $122.90  
  Purchase #2 $178.83   11.688%   $199.7317   $199.73   $199.75   $199.70  
  Purchase #3 $118.94   13.603%   $135.1194   $135.12   $135.10   $135.10  
  Purchase #4 $82.65   12.687%   $93.1358   $93.14   $93.15   $93.10  
  Purchase #5 $175.93   10.401%   $194.2285   $194.23   $194.25   $194.20  
  Purchase #6 $206.85   8.667%   $224.7777   $224.78   $224.80   $224.80  
  Purchase #7 $51.82   3.682%   $53.728   $53.73   $53.75   $53.70  
  7 purchase totals = $929.29       $1,023.5739   $1,023.58   $1,023.65   $1,023.50