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 $194.63   11.372%   $216.7633   $216.76   $216.75   $216.80  
  Purchase #2 $185.89   5.364%   $195.8611   $195.86   $195.85   $195.90  
  Purchase #3 $169.55   12.751%   $191.1693   $191.17   $191.15   $191.20  
  Purchase #4 $152.79   5.377%   $161.0055   $161.01   $161.00   $161.00  
  Purchase #5 $201.68   6.554%   $214.8981   $214.90   $214.90   $214.90  
  Purchase #6 $58.95   5.176%   $62.0013   $62.00   $62.00   $62.00  
  Purchase #7 $220.30   6.165%   $233.8815   $233.88   $233.90   $233.90  
  7 purchase totals = $1,183.79       $1,275.5801   $1,275.58   $1,275.55   $1,275.70