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	$151.33	5.330%	$159.3959	$159.40	$159.40	$159.40
Purchase #2	$99.90	11.539%	$111.4275	$111.43	$111.45	$111.40
Purchase #3	$145.61	8.683%	$158.2533	$158.25	$158.25	$158.30
Purchase #4	$44.96	12.375%	$50.5238	$50.52	$50.50	$50.50
Purchase #5	$120.30	8.422%	$130.4317	$130.43	$130.45	$130.40
Purchase #6	$176.89	11.243%	$196.7777	$196.78	$196.80	$196.80
Purchase #7	$138.66	11.278%	$154.2981	$154.30	$154.30	$154.30
7 purchase totals =	$877.65		$961.1080	$961.11	$961.15	$961.10