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	$48.78	3.680%	$50.5751	$50.58	$50.60	$50.60
Purchase #2	$233.75	9.303%	$255.4958	$255.50	$255.50	$255.50
Purchase #3	$229.79	11.550%	$256.3307	$256.33	$256.35	$256.30
Purchase #4	$161.76	7.427%	$173.7739	$173.77	$173.75	$173.80
Purchase #5	$185.37	6.426%	$197.2819	$197.28	$197.30	$197.30
Purchase #6	$240.47	6.286%	$255.5859	$255.59	$255.60	$255.60
Purchase #7	$216.34	12.839%	$244.1159	$244.12	$244.10	$244.10
7 purchase totals =	$1,316.26		$1,433.1592	$1,433.17	$1,433.20	$1,433.20