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 $62.73   8.383%   $67.9887   $67.99   $68.00   $68.00  
  Purchase #2 $187.42   4.420%   $195.704   $195.70   $195.70   $195.70  
  Purchase #3 $234.25   6.596%   $249.7011   $249.70   $249.70   $249.70  
  Purchase #4 $51.62   12.144%   $57.8887   $57.89   $57.90   $57.90  
  Purchase #5 $196.57   8.236%   $212.7595   $212.76   $212.75   $212.80  
  Purchase #6 $144.84   11.489%   $161.4807   $161.48   $161.50   $161.50  
  Purchase #7 $107.61   5.844%   $113.8987   $113.90   $113.90   $113.90  
  7 purchase totals = $985.04       $1,059.4214   $1,059.42   $1,059.45   $1,059.50