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 $214.87   9.600%   $235.4975   $235.50   $235.50   $235.50  
  Purchase #2 $217.61   9.339%   $237.9326   $237.93   $237.95   $237.90  
  Purchase #3 $29.31   13.758%   $33.3425   $33.34   $33.35   $33.30  
  Purchase #4 $188.97   9.232%   $206.4157   $206.42   $206.40   $206.40  
  Purchase #5 $187.49   5.555%   $197.9051   $197.91   $197.90   $197.90  
  Purchase #6 $167.43   12.256%   $187.9502   $187.95   $187.95   $188.00  
  Purchase #7 $193.46   6.662%   $206.3483   $206.35   $206.35   $206.30  
  7 purchase totals = $1,199.14       $1,305.3919   $1,305.40   $1,305.40   $1,305.30