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 $222.50   5.604%   $234.9689   $234.97   $234.95   $235.00  
  Purchase #2 $51.32   5.163%   $53.9697   $53.97   $53.95   $54.00  
  Purchase #3 $186.96   12.433%   $210.2047   $210.20   $210.20   $210.20  
  Purchase #4 $31.95   7.848%   $34.4574   $34.46   $34.45   $34.50  
  Purchase #5 $119.69   6.428%   $127.3837   $127.38   $127.40   $127.40  
  Purchase #6 $43.40   10.686%   $48.0377   $48.04   $48.05   $48.00  
  Purchase #7 $21.96   5.735%   $23.2194   $23.22   $23.20   $23.20  
  7 purchase totals = $677.78       $732.2415   $732.24   $732.20   $732.30