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 $89.57   5.841%   $94.8018   $94.80   $94.80   $94.80  
  Purchase #2 $187.99   6.194%   $199.6341   $199.63   $199.65   $199.60  
  Purchase #3 $38.67   8.820%   $42.0807   $42.08   $42.10   $42.10  
  Purchase #4 $186.95   4.614%   $195.5759   $195.58   $195.60   $195.60  
  Purchase #5 $115.48   8.563%   $125.3686   $125.37   $125.35   $125.40  
  Purchase #6 $23.96   8.862%   $26.0833   $26.08   $26.10   $26.10  
  Purchase #7 $66.38   3.443%   $68.6655   $68.67   $68.65   $68.70  
  7 purchase totals = $709.00       $752.2099   $752.21   $752.25   $752.30