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 $60.36   11.206%   $67.1239   $67.12   $67.10   $67.10  
  Purchase #2 $43.57   6.668%   $46.4752   $46.48   $46.50   $46.50  
  Purchase #3 $160.88   9.479%   $176.1298   $176.13   $176.15   $176.10  
  Purchase #4 $160.52   9.684%   $176.0648   $176.06   $176.05   $176.10  
  Purchase #5 $218.80   3.267%   $225.9482   $225.95   $225.95   $225.90  
  Purchase #6 $122.77   4.195%   $127.9202   $127.92   $127.90   $127.90  
  Purchase #7 $127.25   6.355%   $135.3367   $135.34   $135.35   $135.30  
  7 purchase totals = $894.15       $954.9988   $955.00   $955.00   $954.90