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 $57.62   7.787%   $62.1069   $62.11   $62.10   $62.10  
  Purchase #2 $205.52   5.750%   $217.3374   $217.34   $217.35   $217.30  
  Purchase #3 $108.34   11.614%   $120.9226   $120.92   $120.90   $120.90  
  Purchase #4 $114.45   9.130%   $124.8993   $124.90   $124.90   $124.90  
  Purchase #5 $224.43   3.725%   $232.79   $232.79   $232.80   $232.80  
  Purchase #6 $29.28   4.283%   $30.5341   $30.53   $30.55   $30.50  
  Purchase #7 $160.80   3.255%   $166.034   $166.03   $166.05   $166.00  
  7 purchase totals = $900.44       $954.6243   $954.62   $954.65   $954.50