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	$106.57	11.532%	$118.8597	$118.86	$118.85	$118.90
Purchase #2	$62.31	7.347%	$66.8879	$66.89	$66.90	$66.90
Purchase #3	$97.25	8.470%	$105.4871	$105.49	$105.50	$105.50
Purchase #4	$7.44	8.439%	$8.0679	$8.07	$8.05	$8.10
Purchase #5	$167.25	3.114%	$172.4582	$172.46	$172.45	$172.50
Purchase #6	$68.27	10.643%	$75.536	$75.54	$75.55	$75.50
Purchase #7	$82.43	7.858%	$88.9073	$88.91	$88.90	$88.90
7 purchase totals =	$591.52		$636.2041	$636.22	$636.20	$636.30