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	$64.46	13.592%	$73.2214	$73.22	$73.20	$73.20
Purchase #2	$112.95	12.733%	$127.3319	$127.33	$127.35	$127.30
Purchase #3	$142.52	6.208%	$151.3676	$151.37	$151.35	$151.40
Purchase #4	$210.92	5.383%	$222.2738	$222.27	$222.25	$222.30
Purchase #5	$10.50	8.751%	$11.4189	$11.42	$11.40	$11.40
Purchase #6	$66.42	12.217%	$74.5345	$74.53	$74.55	$74.50
Purchase #7	$67.63	13.545%	$76.7905	$76.79	$76.80	$76.80
7 purchase totals =	$675.40		$736.9386	$736.93	$736.90	$736.90