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	$95.39	8.147%	$103.1614	$103.16	$103.15	$103.20
Purchase #2	$220.78	5.123%	$232.0906	$232.09	$232.10	$232.10
Purchase #3	$184.65	10.565%	$204.1583	$204.16	$204.15	$204.20
Purchase #4	$37.29	5.627%	$39.3883	$39.39	$39.40	$39.40
Purchase #5	$158.86	8.593%	$172.5108	$172.51	$172.50	$172.50
Purchase #6	$237.73	4.662%	$248.813	$248.81	$248.80	$248.80
Purchase #7	$146.66	13.412%	$166.33	$166.33	$166.35	$166.30
7 purchase totals =	$1,081.36		$1,166.4524	$1,166.45	$1,166.45	$1,166.50