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 $213.98   13.376%   $242.602   $242.60   $242.60   $242.60  
  Purchase #2 $167.63   11.592%   $187.0617   $187.06   $187.05   $187.10  
  Purchase #3 $146.34   5.495%   $154.3814   $154.38   $154.40   $154.40  
  Purchase #4 $201.43   12.492%   $226.5926   $226.59   $226.60   $226.60  
  Purchase #5 $7.51   13.559%   $8.5283   $8.53   $8.55   $8.50  
  Purchase #6 $146.76   7.199%   $157.3253   $157.33   $157.35   $157.30  
  Purchase #7 $212.42   5.841%   $224.8275   $224.83   $224.85   $224.80  
  7 purchase totals = $1,096.07       $1,201.3188   $1,201.32   $1,201.40   $1,201.30