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 $208.32   13.130%   $235.6724   $235.67   $235.65   $235.70  
  Purchase #2 $8.86   9.590%   $9.7097   $9.71   $9.70   $9.70  
  Purchase #3 $47.88   9.370%   $52.3664   $52.37   $52.35   $52.40  
  Purchase #4 $106.77   9.121%   $116.5085   $116.51   $116.50   $116.50  
  Purchase #5 $103.54   8.586%   $112.4299   $112.43   $112.45   $112.40  
  Purchase #6 $153.46   13.785%   $174.6145   $174.61   $174.60   $174.60  
  Purchase #7 $215.68   7.476%   $231.8042   $231.80   $231.80   $231.80  
  7 purchase totals = $844.51       $933.1056   $933.10   $933.05   $933.10