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	$100.69	11.103%	$111.8696	$111.87	$111.85	$111.90
Purchase #2	$111.87	4.664%	$117.0876	$117.09	$117.10	$117.10
Purchase #3	$33.38	10.610%	$36.9216	$36.92	$36.90	$36.90
Purchase #4	$70.30	10.723%	$77.8383	$77.84	$77.85	$77.80
Purchase #5	$250.40	10.632%	$277.0225	$277.02	$277.00	$277.00
Purchase #6	$149.72	13.190%	$169.4681	$169.47	$169.45	$169.50
Purchase #7	$71.86	4.476%	$75.0765	$75.08	$75.10	$75.10
7 purchase totals =	$788.22		$865.2842	$865.29	$865.25	$865.30