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 $68.64   11.636%   $76.627   $76.63   $76.65   $76.60  
  Purchase #2 $233.39   8.323%   $252.815   $252.82   $252.80   $252.80  
  Purchase #3 $87.89   7.466%   $94.4519   $94.45   $94.45   $94.50  
  Purchase #4 $246.69   5.116%   $259.3107   $259.31   $259.30   $259.30  
  Purchase #5 $54.28   10.767%   $60.1243   $60.12   $60.10   $60.10  
  Purchase #6 $105.61   10.123%   $116.3009   $116.30   $116.30   $116.30  
  Purchase #7 $22.84   7.554%   $24.5653   $24.57   $24.55   $24.60  
  7 purchase totals = $819.34       $884.1951   $884.20   $884.15   $884.20