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 $82.71   13.171%   $93.6037   $93.60   $93.60   $93.60  
  Purchase #2 $189.35   3.681%   $196.32   $196.32   $196.30   $196.30  
  Purchase #3 $146.69   8.254%   $158.7978   $158.80   $158.80   $158.80  
  Purchase #4 $62.71   10.465%   $69.2726   $69.27   $69.25   $69.30  
  Purchase #5 $13.30   7.874%   $14.3472   $14.35   $14.35   $14.30  
  Purchase #6 $81.85   6.746%   $87.3716   $87.37   $87.35   $87.40  
  Purchase #7 $220.88   10.617%   $244.3308   $244.33   $244.35   $244.30  
  7 purchase totals = $797.49       $864.0437   $864.04   $864.00   $864.00