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	$227.50	10.446%	$251.2647	$251.26	$251.25	$251.30
Purchase #2	$225.52	7.821%	$243.1579	$243.16	$243.15	$243.20
Purchase #3	$229.26	9.237%	$250.4367	$250.44	$250.45	$250.40
Purchase #4	$89.58	10.314%	$98.8193	$98.82	$98.80	$98.80
Purchase #5	$28.62	13.454%	$32.4705	$32.47	$32.45	$32.50
Purchase #6	$10.68	8.261%	$11.5623	$11.56	$11.55	$11.60
Purchase #7	$200.45	5.849%	$212.1743	$212.17	$212.15	$212.20
7 purchase totals =	$1,011.61		$1,099.8857	$1,099.88	$1,099.80	$1,100.00