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	$129.30	13.643%	$146.9404	$146.94	$146.95	$146.90
Purchase #2	$152.25	4.277%	$158.7617	$158.76	$158.75	$158.80
Purchase #3	$99.92	11.586%	$111.4967	$111.50	$111.50	$111.50
Purchase #4	$241.43	7.663%	$259.9308	$259.93	$259.95	$259.90
Purchase #5	$240.47	13.438%	$272.7844	$272.78	$272.80	$272.80
Purchase #6	$133.47	13.473%	$151.4524	$151.45	$151.45	$151.50
Purchase #7	$22.74	4.579%	$23.7813	$23.78	$23.80	$23.80
7 purchase totals =	$1,019.58		$1,125.1477	$1,125.14	$1,125.20	$1,125.20