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 $236.34   7.639%   $254.394   $254.39   $254.40   $254.40  
  Purchase #2 $79.60   11.431%   $88.6991   $88.70   $88.70   $88.70  
  Purchase #3 $54.31   11.790%   $60.7131   $60.71   $60.70   $60.70  
  Purchase #4 $73.94   3.863%   $76.7963   $76.80   $76.80   $76.80  
  Purchase #5 $209.25   4.420%   $218.4989   $218.50   $218.50   $218.50  
  Purchase #6 $49.64   11.640%   $55.4181   $55.42   $55.40   $55.40  
  Purchase #7 $245.91   5.787%   $260.1408   $260.14   $260.15   $260.10  
  7 purchase totals = $948.99       $1,014.6603   $1,014.66   $1,014.65   $1,014.60