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	$162.52	7.381%	$174.5156	$174.52	$174.50	$174.50
Purchase #2	$78.76	9.273%	$86.0634	$86.06	$86.05	$86.10
Purchase #3	$88.66	8.176%	$95.9088	$95.91	$95.90	$95.90
Purchase #4	$239.81	13.167%	$271.3858	$271.39	$271.40	$271.40
Purchase #5	$142.52	6.366%	$151.5928	$151.59	$151.60	$151.60
Purchase #6	$66.83	6.494%	$71.1699	$71.17	$71.15	$71.20
Purchase #7	$23.29	12.198%	$26.1309	$26.13	$26.15	$26.10
7 purchase totals =	$802.39		$876.7672	$876.77	$876.75	$876.80