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 $166.53   11.703%   $186.019   $186.02   $186.00   $186.00  
  Purchase #2 $44.74   3.445%   $46.2813   $46.28   $46.30   $46.30  
  Purchase #3 $93.89   8.609%   $101.973   $101.97   $101.95   $102.00  
  Purchase #4 $56.51   3.772%   $58.6416   $58.64   $58.65   $58.60  
  Purchase #5 $16.49   11.696%   $18.4187   $18.42   $18.40   $18.40  
  Purchase #6 $245.51   7.502%   $263.9282   $263.93   $263.95   $263.90  
  Purchase #7 $154.30   11.513%   $172.0646   $172.06   $172.05   $172.10  
  7 purchase totals = $777.97       $847.3264   $847.32   $847.30   $847.30