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	$230.76	9.243%	$252.0891	$252.09	$252.10	$252.10
Purchase #2	$190.79	13.631%	$216.7966	$216.80	$216.80	$216.80
Purchase #3	$22.50	4.792%	$23.5782	$23.58	$23.60	$23.60
Purchase #4	$87.75	13.182%	$99.3172	$99.32	$99.30	$99.30
Purchase #5	$105.60	7.786%	$113.822	$113.82	$113.80	$113.80
Purchase #6	$230.42	6.582%	$245.5862	$245.59	$245.60	$245.60
Purchase #7	$55.69	10.475%	$61.5235	$61.52	$61.50	$61.50
7 purchase totals =	$923.51		$1,012.7128	$1,012.72	$1,012.70	$1,012.70