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 $133.51   7.555%   $143.5967   $143.60   $143.60   $143.60  
  Purchase #2 $86.44   10.156%   $95.2188   $95.22   $95.20   $95.20  
  Purchase #3 $98.64   8.293%   $106.8202   $106.82   $106.80   $106.80  
  Purchase #4 $194.87   5.813%   $206.1978   $206.20   $206.20   $206.20  
  Purchase #5 $48.28   9.763%   $52.9936   $52.99   $53.00   $53.00  
  Purchase #6 $53.78   6.424%   $57.2348   $57.23   $57.25   $57.20  
  Purchase #7 $94.81   3.382%   $98.0165   $98.02   $98.00   $98.00  
  7 purchase totals = $710.33       $760.0784   $760.08   $760.05   $760.00