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	$132.67	10.359%	$146.4133	$146.41	$146.40	$146.40
Purchase #2	$156.82	6.862%	$167.581	$167.58	$167.60	$167.60
Purchase #3	$118.35	11.607%	$132.0869	$132.09	$132.10	$132.10
Purchase #4	$66.74	8.245%	$72.2427	$72.24	$72.25	$72.20
Purchase #5	$141.30	7.741%	$152.238	$152.24	$152.25	$152.20
Purchase #6	$48.85	9.149%	$53.3193	$53.32	$53.30	$53.30
Purchase #7	$134.27	9.517%	$147.0485	$147.05	$147.05	$147.00
7 purchase totals =	$799.00		$870.9297	$870.93	$870.95	$870.80