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 $182.47   7.353%   $195.887   $195.89   $195.90   $195.90  
  Purchase #2 $49.83   4.246%   $51.9458   $51.95   $51.95   $51.90  
  Purchase #3 $20.49   12.509%   $23.0531   $23.05   $23.05   $23.10  
  Purchase #4 $64.65   3.779%   $67.0931   $67.09   $67.10   $67.10  
  Purchase #5 $222.73   4.143%   $231.9577   $231.96   $231.95   $232.00  
  Purchase #6 $120.40   5.230%   $126.6969   $126.70   $126.70   $126.70  
  Purchase #7 $127.73   7.123%   $136.8282   $136.83   $136.85   $136.80  
  7 purchase totals = $788.30       $833.4618   $833.47   $833.50   $833.50