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	$115.41	10.433%	$127.4507	$127.45	$127.45	$127.50
Purchase #2	$10.26	10.426%	$11.3297	$11.33	$11.35	$11.30
Purchase #3	$172.36	7.712%	$185.6524	$185.65	$185.65	$185.70
Purchase #4	$202.89	11.132%	$225.4757	$225.48	$225.50	$225.50
Purchase #5	$43.40	13.568%	$49.2885	$49.29	$49.30	$49.30
Purchase #6	$32.92	5.564%	$34.7517	$34.75	$34.75	$34.80
Purchase #7	$53.91	4.820%	$56.5085	$56.51	$56.50	$56.50
7 purchase totals =	$631.15		$690.4572	$690.46	$690.50	$690.60