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	$224.46	8.518%	$243.5795	$243.58	$243.60	$243.60
Purchase #2	$58.49	5.699%	$61.8233	$61.82	$61.80	$61.80
Purchase #3	$30.54	6.431%	$32.504	$32.50	$32.50	$32.50
Purchase #4	$42.42	4.232%	$44.2152	$44.22	$44.20	$44.20
Purchase #5	$224.29	13.495%	$254.5579	$254.56	$254.55	$254.60
Purchase #6	$28.80	4.570%	$30.1162	$30.12	$30.10	$30.10
Purchase #7	$92.28	7.780%	$99.4594	$99.46	$99.45	$99.50
7 purchase totals =	$701.28		$766.2555	$766.26	$766.20	$766.30