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	$95.38	10.709%	$105.5942	$105.59	$105.60	$105.60
Purchase #2	$158.82	13.262%	$179.8827	$179.88	$179.90	$179.90
Purchase #3	$207.41	10.724%	$229.6526	$229.65	$229.65	$229.70
Purchase #4	$155.87	6.435%	$165.9002	$165.90	$165.90	$165.90
Purchase #5	$185.66	3.733%	$192.5907	$192.59	$192.60	$192.60
Purchase #6	$195.29	6.866%	$208.6986	$208.70	$208.70	$208.70
Purchase #7	$130.70	12.819%	$147.4544	$147.45	$147.45	$147.50
7 purchase totals =	$1,129.13		$1,229.7734	$1,229.76	$1,229.80	$1,229.90