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	$220.70	12.156%	$247.5283	$247.53	$247.55	$247.50
Purchase #2	$244.91	11.721%	$273.6159	$273.62	$273.60	$273.60
Purchase #3	$63.37	11.466%	$70.636	$70.64	$70.65	$70.60
Purchase #4	$103.29	7.735%	$111.2795	$111.28	$111.30	$111.30
Purchase #5	$124.99	7.558%	$134.4367	$134.44	$134.45	$134.40
Purchase #6	$143.68	3.174%	$148.2404	$148.24	$148.25	$148.20
Purchase #7	$75.75	8.612%	$82.2736	$82.27	$82.25	$82.30
7 purchase totals =	$976.69		$1,068.0104	$1,068.02	$1,068.05	$1,067.90