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	$149.59	11.808%	$167.2536	$167.25	$167.25	$167.30
Purchase #2	$199.95	11.485%	$222.9143	$222.91	$222.90	$222.90
Purchase #3	$153.31	11.452%	$170.8671	$170.87	$170.85	$170.90
Purchase #4	$100.92	7.838%	$108.8301	$108.83	$108.85	$108.80
Purchase #5	$155.72	11.502%	$173.6309	$173.63	$173.65	$173.60
Purchase #6	$46.38	5.380%	$48.8752	$48.88	$48.90	$48.90
Purchase #7	$211.84	5.688%	$223.8895	$223.89	$223.90	$223.90
7 purchase totals =	$1,017.71		$1,116.2607	$1,116.26	$1,116.30	$1,116.30