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	$98.25	13.758%	$111.7672	$111.77	$111.75	$111.80
Purchase #2	$165.88	8.461%	$179.9151	$179.92	$179.90	$179.90
Purchase #3	$227.73	10.108%	$250.7489	$250.75	$250.75	$250.70
Purchase #4	$165.49	13.388%	$187.6458	$187.65	$187.65	$187.60
Purchase #5	$175.47	8.405%	$190.2183	$190.22	$190.20	$190.20
Purchase #6	$166.35	6.167%	$176.6088	$176.61	$176.60	$176.60
Purchase #7	$113.26	12.589%	$127.5183	$127.52	$127.50	$127.50
7 purchase totals =	$1,112.43		$1,224.4224	$1,224.44	$1,224.35	$1,224.30