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	$165.27	12.305%	$185.6065	$185.61	$185.60	$185.60
Purchase #2	$30.39	6.222%	$32.2809	$32.28	$32.30	$32.30
Purchase #3	$47.80	10.176%	$52.6641	$52.66	$52.65	$52.70
Purchase #4	$195.98	13.592%	$222.6176	$222.62	$222.60	$222.60
Purchase #5	$126.87	4.246%	$132.2569	$132.26	$132.25	$132.30
Purchase #6	$191.58	13.463%	$217.3724	$217.37	$217.35	$217.40
Purchase #7	$59.49	13.135%	$67.304	$67.30	$67.30	$67.30
7 purchase totals =	$817.38		$910.1024	$910.10	$910.05	$910.20