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 $206.57   5.275%   $217.4666   $217.47   $217.45   $217.50  
  Purchase #2 $189.43   5.374%   $199.61   $199.61   $199.60   $199.60  
  Purchase #3 $87.43   8.227%   $94.6229   $94.62   $94.60   $94.60  
  Purchase #4 $239.56   13.779%   $272.569   $272.57   $272.55   $272.60  
  Purchase #5 $9.77   11.391%   $10.8829   $10.88   $10.90   $10.90  
  Purchase #6 $122.68   8.851%   $133.5384   $133.54   $133.55   $133.50  
  Purchase #7 $249.80   5.211%   $262.8171   $262.82   $262.80   $262.80  
  7 purchase totals = $1,105.24       $1,191.5069   $1,191.51   $1,191.45   $1,191.50