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 $32.44   7.350%   $34.8243   $34.82   $34.80   $34.80  
  Purchase #2 $166.73   5.834%   $176.457   $176.46   $176.45   $176.50  
  Purchase #3 $110.63   10.176%   $121.8877   $121.89   $121.90   $121.90  
  Purchase #4 $172.39   6.730%   $183.9918   $183.99   $184.00   $184.00  
  Purchase #5 $16.77   5.123%   $17.6291   $17.63   $17.65   $17.60  
  Purchase #6 $212.57   6.557%   $226.5082   $226.51   $226.50   $226.50  
  Purchase #7 $194.74   3.312%   $201.1898   $201.19   $201.20   $201.20  
  7 purchase totals = $906.27       $962.4879   $962.49   $962.50   $962.50