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 $91.61   5.375%   $96.534   $96.53   $96.55   $96.50  
  Purchase #2 $161.77   3.327%   $167.1521   $167.15   $167.15   $167.20  
  Purchase #3 $227.65   7.598%   $244.9468   $244.95   $244.95   $244.90  
  Purchase #4 $28.29   8.183%   $30.605   $30.61   $30.60   $30.60  
  Purchase #5 $174.94   8.125%   $189.1539   $189.15   $189.15   $189.20  
  Purchase #6 $244.86   13.788%   $278.6213   $278.62   $278.60   $278.60  
  Purchase #7 $64.38   7.498%   $69.2072   $69.21   $69.20   $69.20  
  7 purchase totals = $993.50       $1,076.2203   $1,076.22   $1,076.20   $1,076.20