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 $151.98   6.769%   $162.2675   $162.27   $162.25   $162.30  
  Purchase #2 $233.71   13.450%   $265.144   $265.14   $265.15   $265.10  
  Purchase #3 $152.78   11.162%   $169.8333   $169.83   $169.85   $169.80  
  Purchase #4 $46.27   3.859%   $48.0556   $48.06   $48.05   $48.10  
  Purchase #5 $69.97   5.480%   $73.8044   $73.80   $73.80   $73.80  
  Purchase #6 $153.43   10.747%   $169.9191   $169.92   $169.90   $169.90  
  Purchase #7 $125.34   6.740%   $133.7879   $133.79   $133.80   $133.80  
  7 purchase totals = $933.48       $1,022.8118   $1,022.81   $1,022.80   $1,022.80