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 $119.41   5.696%   $126.2116   $126.21   $126.20   $126.20  
  Purchase #2 $211.45   6.767%   $225.7588   $225.76   $225.75   $225.80  
  Purchase #3 $192.30   8.135%   $207.9436   $207.94   $207.95   $207.90  
  Purchase #4 $242.39   8.591%   $263.2137   $263.21   $263.20   $263.20  
  Purchase #5 $45.64   7.744%   $49.1744   $49.17   $49.15   $49.20  
  Purchase #6 $221.46   4.820%   $232.1344   $232.13   $232.15   $232.10  
  Purchase #7 $185.41   7.573%   $199.4511   $199.45   $199.45   $199.50  
  7 purchase totals = $1,218.06       $1,303.8876   $1,303.87   $1,303.85   $1,303.90