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 $109.38   9.278%   $119.5283   $119.53   $119.55   $119.50  
  Purchase #2 $239.97   9.295%   $262.2752   $262.28   $262.30   $262.30  
  Purchase #3 $41.28   12.548%   $46.4598   $46.46   $46.45   $46.50  
  Purchase #4 $66.91   12.353%   $75.1754   $75.18   $75.20   $75.20  
  Purchase #5 $127.71   4.548%   $133.5183   $133.52   $133.50   $133.50  
  Purchase #6 $249.85   8.373%   $270.7699   $270.77   $270.75   $270.80  
  Purchase #7 $142.71   6.485%   $151.9647   $151.96   $151.95   $152.00  
  7 purchase totals = $977.81       $1,059.6916   $1,059.70   $1,059.70   $1,059.80