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 $119.54   5.652%   $126.2964   $126.30   $126.30   $126.30  
  Purchase #2 $233.33   11.264%   $259.6123   $259.61   $259.60   $259.60  
  Purchase #3 $10.54   11.562%   $11.7586   $11.76   $11.75   $11.80  
  Purchase #4 $249.53   10.826%   $276.5441   $276.54   $276.55   $276.50  
  Purchase #5 $66.79   5.131%   $70.217   $70.22   $70.20   $70.20  
  Purchase #6 $41.93   6.264%   $44.5565   $44.56   $44.55   $44.60  
  Purchase #7 $172.85   3.733%   $179.3025   $179.30   $179.30   $179.30  
  7 purchase totals = $894.51       $968.2874   $968.29   $968.25   $968.30