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 $148.71   3.428%   $153.8078   $153.81   $153.80   $153.80  
  Purchase #2 $152.93   9.602%   $167.6143   $167.61   $167.60   $167.60  
  Purchase #3 $90.87   3.133%   $93.717   $93.72   $93.70   $93.70  
  Purchase #4 $14.51   12.197%   $16.2798   $16.28   $16.30   $16.30  
  Purchase #5 $223.75   5.481%   $236.0137   $236.01   $236.00   $236.00  
  Purchase #6 $175.26   10.635%   $193.8989   $193.90   $193.90   $193.90  
  Purchase #7 $149.56   8.292%   $161.9615   $161.96   $161.95   $162.00  
  7 purchase totals = $955.59       $1,023.2930   $1,023.29   $1,023.25   $1,023.30