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 $93.42   13.527%   $106.0569   $106.06   $106.05   $106.10  
  Purchase #2 $217.96   12.863%   $245.9962   $246.00   $246.00   $246.00  
  Purchase #3 $96.98   9.178%   $105.8808   $105.88   $105.90   $105.90  
  Purchase #4 $57.69   11.328%   $64.2251   $64.23   $64.25   $64.20  
  Purchase #5 $151.34   9.639%   $165.9277   $165.93   $165.95   $165.90  
  Purchase #6 $224.88   7.252%   $241.1883   $241.19   $241.20   $241.20  
  Purchase #7 $214.91   12.389%   $241.5352   $241.54   $241.55   $241.50  
  7 purchase totals = $1,057.18       $1,170.8102   $1,170.83   $1,170.90   $1,170.80