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 $162.41   6.725%   $173.3321   $173.33   $173.35   $173.30  
  Purchase #2 $231.25   10.249%   $254.9508   $254.95   $254.95   $255.00  
  Purchase #3 $247.34   8.204%   $267.6318   $267.63   $267.65   $267.60  
  Purchase #4 $143.87   7.312%   $154.3898   $154.39   $154.40   $154.40  
  Purchase #5 $51.49   9.463%   $56.3625   $56.36   $56.35   $56.40  
  Purchase #6 $33.75   9.447%   $36.9384   $36.94   $36.95   $36.90  
  Purchase #7 $168.90   8.795%   $183.7548   $183.75   $183.75   $183.80  
  7 purchase totals = $1,039.01       $1,127.3602   $1,127.35   $1,127.40   $1,127.40