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 $182.42   10.585%   $201.7292   $201.73   $201.75   $201.70  
  Purchase #2 $87.81   4.329%   $91.6113   $91.61   $91.60   $91.60  
  Purchase #3 $92.68   5.774%   $98.0313   $98.03   $98.05   $98.00  
  Purchase #4 $185.43   7.406%   $199.1629   $199.16   $199.15   $199.20  
  Purchase #5 $131.45   13.867%   $149.6782   $149.68   $149.70   $149.70  
  Purchase #6 $231.96   13.275%   $262.7527   $262.75   $262.75   $262.80  
  Purchase #7 $190.42   7.432%   $204.572   $204.57   $204.55   $204.60  
  7 purchase totals = $1,102.17       $1,207.5376   $1,207.53   $1,207.55   $1,207.60