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 $236.96   10.258%   $261.2674   $261.27   $261.25   $261.30  
  Purchase #2 $169.67   3.428%   $175.4863   $175.49   $175.50   $175.50  
  Purchase #3 $111.90   7.418%   $120.2007   $120.20   $120.20   $120.20  
  Purchase #4 $139.77   3.570%   $144.7598   $144.76   $144.75   $144.80  
  Purchase #5 $108.84   9.415%   $119.0873   $119.09   $119.10   $119.10  
  Purchase #6 $218.42   12.183%   $245.0301   $245.03   $245.05   $245.00  
  Purchase #7 $40.63   8.761%   $44.1896   $44.19   $44.20   $44.20  
  7 purchase totals = $1,026.19       $1,110.0212   $1,110.03   $1,110.05   $1,110.10