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 $211.82   11.344%   $235.8489   $235.85   $235.85   $235.80  
  Purchase #2 $211.71   4.197%   $220.5955   $220.60   $220.60   $220.60  
  Purchase #3 $112.96   5.452%   $119.1186   $119.12   $119.10   $119.10  
  Purchase #4 $158.79   6.176%   $168.5969   $168.60   $168.60   $168.60  
  Purchase #5 $190.71   3.496%   $197.3772   $197.38   $197.40   $197.40  
  Purchase #6 $213.59   9.338%   $233.535   $233.54   $233.55   $233.50  
  Purchase #7 $170.87   3.758%   $177.2913   $177.29   $177.30   $177.30  
  7 purchase totals = $1,270.45       $1,352.3634   $1,352.38   $1,352.40   $1,352.30