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	$11.68	5.143%	$12.2807	$12.28	$12.30	$12.30
Purchase #2	$52.71	3.695%	$54.6576	$54.66	$54.65	$54.70
Purchase #3	$180.35	11.185%	$200.5221	$200.52	$200.50	$200.50
Purchase #4	$34.47	4.775%	$36.1159	$36.12	$36.10	$36.10
Purchase #5	$84.56	7.778%	$91.1371	$91.14	$91.15	$91.10
Purchase #6	$82.50	7.806%	$88.94	$88.94	$88.95	$88.90
Purchase #7	$37.87	12.452%	$42.5856	$42.59	$42.60	$42.60
7 purchase totals =	$484.14		$526.2390	$526.25	$526.25	$526.20