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 $67.61   10.659%   $74.8165   $74.82   $74.80   $74.80  
  Purchase #2 $154.61   7.808%   $166.6819   $166.68   $166.70   $166.70  
  Purchase #3 $217.49   13.274%   $246.3596   $246.36   $246.35   $246.40  
  Purchase #4 $161.26   9.802%   $177.0667   $177.07   $177.05   $177.10  
  Purchase #5 $185.46   3.286%   $191.5542   $191.55   $191.55   $191.60  
  Purchase #6 $21.95   8.131%   $23.7348   $23.73   $23.75   $23.70  
  Purchase #7 $205.66   4.486%   $214.8859   $214.89   $214.90   $214.90  
  7 purchase totals = $1,014.04       $1,095.0996   $1,095.10   $1,095.10   $1,095.20