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 $91.48   4.403%   $95.5079   $95.51   $95.50   $95.50  
  Purchase #2 $222.81   9.641%   $244.2911   $244.29   $244.30   $244.30  
  Purchase #3 $154.29   4.810%   $161.7113   $161.71   $161.70   $161.70  
  Purchase #4 $73.61   11.312%   $81.9368   $81.94   $81.95   $81.90  
  Purchase #5 $241.91   7.355%   $259.7025   $259.70   $259.70   $259.70  
  Purchase #6 $228.43   3.725%   $236.939   $236.94   $236.95   $236.90  
  Purchase #7 $155.99   7.749%   $168.0777   $168.08   $168.10   $168.10  
  7 purchase totals = $1,168.52       $1,248.1663   $1,248.17   $1,248.20   $1,248.10