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	$247.72	8.551%	$268.9025	$268.90	$268.90	$268.90
Purchase #2	$82.88	10.261%	$91.3843	$91.38	$91.40	$91.40
Purchase #3	$95.45	9.456%	$104.4758	$104.48	$104.50	$104.50
Purchase #4	$59.27	11.310%	$65.9734	$65.97	$65.95	$66.00
Purchase #5	$130.41	11.589%	$145.5232	$145.52	$145.50	$145.50
Purchase #6	$204.95	13.483%	$232.5834	$232.58	$232.60	$232.60
Purchase #7	$168.73	4.772%	$176.7818	$176.78	$176.80	$176.80
7 purchase totals =	$989.41		$1,085.6244	$1,085.61	$1,085.65	$1,085.70