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	$176.51	10.748%	$195.4813	$195.48	$195.50	$195.50
Purchase #2	$48.56	12.567%	$54.6625	$54.66	$54.65	$54.70
Purchase #3	$248.78	13.641%	$282.7161	$282.72	$282.70	$282.70
Purchase #4	$55.73	9.512%	$61.031	$61.03	$61.05	$61.00
Purchase #5	$110.35	6.564%	$117.5934	$117.59	$117.60	$117.60
Purchase #6	$112.76	12.784%	$127.1752	$127.18	$127.20	$127.20
Purchase #7	$34.43	9.222%	$37.6051	$37.61	$37.60	$37.60
7 purchase totals =	$787.12		$876.2646	$876.27	$876.30	$876.30