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	$224.42	13.388%	$254.4653	$254.47	$254.45	$254.50
Purchase #2	$249.58	9.517%	$273.3325	$273.33	$273.35	$273.30
Purchase #3	$138.67	5.553%	$146.3703	$146.37	$146.35	$146.40
Purchase #4	$29.94	8.750%	$32.5598	$32.56	$32.55	$32.60
Purchase #5	$74.71	4.851%	$78.3342	$78.33	$78.35	$78.30
Purchase #6	$37.37	13.771%	$42.5162	$42.52	$42.50	$42.50
Purchase #7	$182.74	6.477%	$194.5761	$194.58	$194.60	$194.60
7 purchase totals =	$937.43		$1,022.1544	$1,022.16	$1,022.15	$1,022.20