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	$141.72	6.667%	$151.1685	$151.17	$151.15	$151.20
Purchase #2	$73.42	5.672%	$77.5844	$77.58	$77.60	$77.60
Purchase #3	$18.66	12.450%	$20.9832	$20.98	$21.00	$21.00
Purchase #4	$149.78	10.520%	$165.5369	$165.54	$165.55	$165.50
Purchase #5	$171.91	6.535%	$183.1443	$183.14	$183.15	$183.10
Purchase #6	$208.90	4.121%	$217.5088	$217.51	$217.50	$217.50
Purchase #7	$249.70	13.160%	$282.5605	$282.56	$282.55	$282.60
7 purchase totals =	$1,014.09		$1,098.4866	$1,098.48	$1,098.50	$1,098.50