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 $184.89   5.839%   $195.6857   $195.69   $195.70   $195.70  
  Purchase #2 $243.45   6.234%   $258.6267   $258.63   $258.65   $258.60  
  Purchase #3 $148.50   3.446%   $153.6173   $153.62   $153.60   $153.60  
  Purchase #4 $158.39   6.282%   $168.3401   $168.34   $168.35   $168.30  
  Purchase #5 $79.86   3.167%   $82.3892   $82.39   $82.40   $82.40  
  Purchase #6 $66.77   13.863%   $76.0263   $76.03   $76.05   $76.00  
  Purchase #7 $5.77   13.563%   $6.5526   $6.55   $6.55   $6.60  
  7 purchase totals = $887.63       $941.2379   $941.25   $941.30   $941.20