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 $228.86   9.151%   $249.803   $249.80   $249.80   $249.80  
  Purchase #2 $244.65   7.673%   $263.422   $263.42   $263.40   $263.40  
  Purchase #3 $246.96   7.476%   $265.4227   $265.42   $265.40   $265.40  
  Purchase #4 $236.34   12.858%   $266.7286   $266.73   $266.75   $266.70  
  Purchase #5 $30.40   7.550%   $32.6952   $32.70   $32.70   $32.70  
  Purchase #6 $53.33   13.403%   $60.4778   $60.48   $60.50   $60.50  
  Purchase #7 $197.67   8.138%   $213.7564   $213.76   $213.75   $213.80  
  7 purchase totals = $1,238.21       $1,352.3057   $1,352.31   $1,352.30   $1,352.30