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	$116.26	9.481%	$127.2826	$127.28	$127.30	$127.30
Purchase #2	$57.96	5.725%	$61.2782	$61.28	$61.30	$61.30
Purchase #3	$91.52	13.500%	$103.8752	$103.88	$103.90	$103.90
Purchase #4	$145.39	4.278%	$151.6098	$151.61	$151.60	$151.60
Purchase #5	$142.73	9.335%	$156.0538	$156.05	$156.05	$156.10
Purchase #6	$119.76	9.174%	$130.7468	$130.75	$130.75	$130.70
Purchase #7	$119.38	12.699%	$134.5401	$134.54	$134.55	$134.50
7 purchase totals =	$793.00		$865.3865	$865.39	$865.45	$865.40