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 $195.40   3.697%   $202.6239   $202.62   $202.60   $202.60  
  Purchase #2 $26.84   13.763%   $30.534   $30.53   $30.55   $30.50  
  Purchase #3 $192.48   3.800%   $199.7942   $199.79   $199.80   $199.80  
  Purchase #4 $66.33   8.806%   $72.171   $72.17   $72.15   $72.20  
  Purchase #5 $250.51   3.422%   $259.0825   $259.08   $259.10   $259.10  
  Purchase #6 $145.85   9.821%   $160.1739   $160.17   $160.15   $160.20  
  Purchase #7 $82.85   11.534%   $92.4059   $92.41   $92.40   $92.40  
  7 purchase totals = $960.26       $1,016.7854   $1,016.77   $1,016.75   $1,016.80