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 $216.93   11.282%   $241.404   $241.40   $241.40   $241.40  
  Purchase #2 $235.71   3.645%   $244.3016   $244.30   $244.30   $244.30  
  Purchase #3 $157.38   8.632%   $170.965   $170.97   $170.95   $171.00  
  Purchase #4 $115.62   5.721%   $122.2346   $122.23   $122.25   $122.20  
  Purchase #5 $108.66   3.129%   $112.06   $112.06   $112.05   $112.10  
  Purchase #6 $44.74   8.528%   $48.5554   $48.56   $48.55   $48.60  
  Purchase #7 $160.65   10.153%   $176.9608   $176.96   $176.95   $177.00  
  7 purchase totals = $1,039.69       $1,116.4814   $1,116.48   $1,116.45   $1,116.60