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 $95.39   3.504%   $98.7325   $98.73   $98.75   $98.70  
  Purchase #2 $207.26   13.262%   $234.7468   $234.75   $234.75   $234.70  
  Purchase #3 $151.27   9.641%   $165.8539   $165.85   $165.85   $165.90  
  Purchase #4 $210.64   9.259%   $230.1432   $230.14   $230.15   $230.10  
  Purchase #5 $13.36   10.524%   $14.766   $14.77   $14.75   $14.80  
  Purchase #6 $242.55   10.379%   $267.7243   $267.72   $267.70   $267.70  
  Purchase #7 $101.50   9.580%   $111.2237   $111.22   $111.20   $111.20  
  7 purchase totals = $1,021.97       $1,123.1904   $1,123.18   $1,123.15   $1,123.10