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	$51.47	7.104%	$55.1264	$55.13	$55.15	$55.10
Purchase #2	$18.91	13.584%	$21.4787	$21.48	$21.50	$21.50
Purchase #3	$56.69	4.686%	$59.3465	$59.35	$59.35	$59.30
Purchase #4	$244.58	8.560%	$265.516	$265.52	$265.50	$265.50
Purchase #5	$44.51	8.329%	$48.2172	$48.22	$48.20	$48.20
Purchase #6	$224.87	12.240%	$252.3941	$252.39	$252.40	$252.40
Purchase #7	$41.66	9.788%	$45.7377	$45.74	$45.75	$45.70
7 purchase totals =	$682.69		$747.8166	$747.83	$747.85	$747.70