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 $198.29   4.734%   $207.677   $207.68   $207.70   $207.70  
  Purchase #2 $225.72   13.365%   $255.8875   $255.89   $255.90   $255.90  
  Purchase #3 $189.64   13.344%   $214.9456   $214.95   $214.95   $214.90  
  Purchase #4 $237.90   10.511%   $262.9057   $262.91   $262.90   $262.90  
  Purchase #5 $114.39   5.578%   $120.7707   $120.77   $120.75   $120.80  
  Purchase #6 $84.25   4.759%   $88.2595   $88.26   $88.25   $88.30  
  Purchase #7 $97.61   4.334%   $101.8404   $101.84   $101.85   $101.80  
  7 purchase totals = $1,147.80       $1,252.2864   $1,252.30   $1,252.30   $1,252.30