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	$144.30	10.452%	$159.3822	$159.38	$159.40	$159.40
Purchase #2	$157.78	6.702%	$168.3544	$168.35	$168.35	$168.40
Purchase #3	$137.61	5.733%	$145.4992	$145.50	$145.50	$145.50
Purchase #4	$206.42	8.178%	$223.301	$223.30	$223.30	$223.30
Purchase #5	$205.31	6.198%	$218.0351	$218.04	$218.05	$218.00
Purchase #6	$59.82	3.114%	$61.6828	$61.68	$61.70	$61.70
Purchase #7	$109.27	8.837%	$118.9262	$118.93	$118.95	$118.90
7 purchase totals =	$1,020.51		$1,095.1809	$1,095.18	$1,095.25	$1,095.20