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 $61.35   9.516%   $67.1881   $67.19   $67.20   $67.20  
  Purchase #2 $248.52   5.670%   $262.6111   $262.61   $262.60   $262.60  
  Purchase #3 $150.93   4.794%   $158.1656   $158.17   $158.15   $158.20  
  Purchase #4 $166.71   6.618%   $177.7429   $177.74   $177.75   $177.70  
  Purchase #5 $140.40   7.532%   $150.9749   $150.97   $150.95   $151.00  
  Purchase #6 $120.53   11.390%   $134.2584   $134.26   $134.25   $134.30  
  Purchase #7 $103.46   8.466%   $112.2189   $112.22   $112.20   $112.20  
  7 purchase totals = $991.90       $1,063.1599   $1,063.16   $1,063.10   $1,063.20