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 $62.85   6.638%   $67.022   $67.02   $67.00   $67.00  
  Purchase #2 $115.83   12.386%   $130.1767   $130.18   $130.20   $130.20  
  Purchase #3 $66.72   10.353%   $73.6275   $73.63   $73.65   $73.60  
  Purchase #4 $39.44   10.812%   $43.7043   $43.70   $43.70   $43.70  
  Purchase #5 $135.81   6.656%   $144.8495   $144.85   $144.85   $144.80  
  Purchase #6 $66.48   3.258%   $68.6459   $68.65   $68.65   $68.60  
  Purchase #7 $209.93   12.725%   $236.6436   $236.64   $236.65   $236.60  
  7 purchase totals = $697.06       $764.6695   $764.67   $764.70   $764.50