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 $84.96   12.117%   $95.2546   $95.25   $95.25   $95.30  
  Purchase #2 $127.61   6.687%   $136.1433   $136.14   $136.15   $136.10  
  Purchase #3 $133.73   10.515%   $147.7917   $147.79   $147.80   $147.80  
  Purchase #4 $166.37   12.733%   $187.5539   $187.55   $187.55   $187.60  
  Purchase #5 $20.87   7.543%   $22.4442   $22.44   $22.45   $22.40  
  Purchase #6 $162.34   9.336%   $177.4961   $177.50   $177.50   $177.50  
  Purchase #7 $250.93   10.472%   $277.2074   $277.21   $277.20   $277.20  
  7 purchase totals = $946.81       $1,043.8912   $1,043.88   $1,043.90   $1,043.90