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 $92.33   3.284%   $95.3621   $95.36   $95.35   $95.40  
  Purchase #2 $247.74   6.299%   $263.3451   $263.35   $263.35   $263.30  
  Purchase #3 $89.42   7.270%   $95.9208   $95.92   $95.90   $95.90  
  Purchase #4 $86.80   3.377%   $89.7312   $89.73   $89.75   $89.70  
  Purchase #5 $117.67   6.829%   $125.7057   $125.71   $125.70   $125.70  
  Purchase #6 $46.73   4.495%   $48.8305   $48.83   $48.85   $48.80  
  Purchase #7 $216.94   12.542%   $244.1486   $244.15   $244.15   $244.10  
  7 purchase totals = $897.63       $963.0440   $963.05   $963.05   $962.90