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 $42.57   9.713%   $46.7048   $46.70   $46.70   $46.70  
  Purchase #2 $46.34   9.399%   $50.6955   $50.70   $50.70   $50.70  
  Purchase #3 $243.33   10.862%   $269.7605   $269.76   $269.75   $269.80  
  Purchase #4 $178.39   13.551%   $202.5636   $202.56   $202.55   $202.60  
  Purchase #5 $59.86   10.136%   $65.9274   $65.93   $65.95   $65.90  
  Purchase #6 $32.84   5.170%   $34.5378   $34.54   $34.55   $34.50  
  Purchase #7 $215.49   4.581%   $225.3616   $225.36   $225.35   $225.40  
  7 purchase totals = $818.82       $895.5512   $895.55   $895.55   $895.60