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 $111.31   7.449%   $119.6015   $119.60   $119.60   $119.60  
  Purchase #2 $150.75   10.391%   $166.4144   $166.41   $166.40   $166.40  
  Purchase #3 $68.49   12.302%   $76.9156   $76.92   $76.90   $76.90  
  Purchase #4 $12.91   9.824%   $14.1783   $14.18   $14.20   $14.20  
  Purchase #5 $207.33   7.332%   $222.5314   $222.53   $222.55   $222.50  
  Purchase #6 $69.77   8.508%   $75.706   $75.71   $75.70   $75.70  
  Purchase #7 $203.49   3.153%   $209.906   $209.91   $209.90   $209.90  
  7 purchase totals = $824.05       $885.2532   $885.26   $885.25   $885.20