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	$115.35	6.873%	$123.278	$123.28	$123.30	$123.30
Purchase #2	$74.57	6.664%	$79.5393	$79.54	$79.55	$79.50
Purchase #3	$74.25	5.561%	$78.379	$78.38	$78.40	$78.40
Purchase #4	$141.88	10.326%	$156.5305	$156.53	$156.55	$156.50
Purchase #5	$209.63	8.660%	$227.784	$227.78	$227.80	$227.80
Purchase #6	$52.51	6.256%	$55.795	$55.80	$55.80	$55.80
Purchase #7	$21.43	9.567%	$23.4802	$23.48	$23.50	$23.50
7 purchase totals =	$689.62		$744.7860	$744.79	$744.90	$744.80