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 $46.81   8.797%   $50.9279   $50.93   $50.95   $50.90  
  Purchase #2 $67.96   4.587%   $71.0773   $71.08   $71.10   $71.10  
  Purchase #3 $140.81   12.241%   $158.0466   $158.05   $158.05   $158.00  
  Purchase #4 $149.55   13.455%   $169.672   $169.67   $169.65   $169.70  
  Purchase #5 $245.50   7.617%   $264.1997   $264.20   $264.20   $264.20  
  Purchase #6 $101.41   13.549%   $115.15   $115.15   $115.15   $115.20  
  Purchase #7 $211.39   6.562%   $225.2614   $225.26   $225.25   $225.30  
  7 purchase totals = $963.43       $1,054.3349   $1,054.34   $1,054.35   $1,054.40