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 $46.47   5.157%   $48.8665   $48.87   $48.85   $48.90  
  Purchase #2 $169.86   5.366%   $178.9747   $178.97   $178.95   $179.00  
  Purchase #3 $60.63   3.314%   $62.6393   $62.64   $62.65   $62.60  
  Purchase #4 $195.66   9.695%   $214.6292   $214.63   $214.65   $214.60  
  Purchase #5 $87.25   9.706%   $95.7185   $95.72   $95.70   $95.70  
  Purchase #6 $76.96   5.252%   $81.0019   $81.00   $81.00   $81.00  
  Purchase #7 $65.72   7.227%   $70.4696   $70.47   $70.45   $70.50  
  7 purchase totals = $702.55       $752.2997   $752.30   $752.25   $752.30