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 $119.68   11.218%   $133.1057   $133.11   $133.10   $133.10  
  Purchase #2 $210.64   12.679%   $237.347   $237.35   $237.35   $237.30  
  Purchase #3 $114.92   10.502%   $126.9889   $126.99   $127.00   $127.00  
  Purchase #4 $61.71   13.237%   $69.8786   $69.88   $69.90   $69.90  
  Purchase #5 $212.97   6.423%   $226.6491   $226.65   $226.65   $226.60  
  Purchase #6 $190.49   4.724%   $199.4887   $199.49   $199.50   $199.50  
  Purchase #7 $112.65   6.667%   $120.1604   $120.16   $120.15   $120.20  
  7 purchase totals = $1,023.06       $1,113.6184   $1,113.63   $1,113.65   $1,113.60