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 $32.85   6.385%   $34.9475   $34.95   $34.95   $34.90  
  Purchase #2 $189.63   4.364%   $197.9055   $197.91   $197.90   $197.90  
  Purchase #3 $159.38   8.554%   $173.0134   $173.01   $173.00   $173.00  
  Purchase #4 $155.70   7.785%   $167.8212   $167.82   $167.80   $167.80  
  Purchase #5 $178.73   11.321%   $198.964   $198.96   $198.95   $199.00  
  Purchase #6 $243.97   11.243%   $271.3995   $271.40   $271.40   $271.40  
  Purchase #7 $166.87   11.486%   $186.0367   $186.04   $186.05   $186.00  
  7 purchase totals = $1,127.13       $1,230.0878   $1,230.09   $1,230.05   $1,230.00