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 $62.62   10.119%   $68.9565   $68.96   $68.95   $69.00  
  Purchase #2 $104.65   4.791%   $109.6638   $109.66   $109.65   $109.70  
  Purchase #3 $225.66   11.290%   $251.137   $251.14   $251.15   $251.10  
  Purchase #4 $112.25   3.348%   $116.0081   $116.01   $116.00   $116.00  
  Purchase #5 $218.98   6.486%   $233.183   $233.18   $233.20   $233.20  
  Purchase #6 $7.49   5.259%   $7.8839   $7.88   $7.90   $7.90  
  Purchase #7 $152.57   6.310%   $162.1972   $162.20   $162.20   $162.20  
  7 purchase totals = $884.22       $949.0295   $949.03   $949.05   $949.10