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 $46.26   5.253%   $48.69   $48.69   $48.70   $48.70  
  Purchase #2 $192.54   13.729%   $218.9738   $218.97   $218.95   $219.00  
  Purchase #3 $48.37   4.696%   $50.6415   $50.64   $50.65   $50.60  
  Purchase #4 $216.56   5.482%   $228.4318   $228.43   $228.45   $228.40  
  Purchase #5 $153.68   10.869%   $170.3835   $170.38   $170.40   $170.40  
  Purchase #6 $149.49   11.778%   $167.0969   $167.10   $167.10   $167.10  
  Purchase #7 $88.26   6.177%   $93.7118   $93.71   $93.70   $93.70  
  7 purchase totals = $895.16       $977.9293   $977.92   $977.95   $977.90