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	$100.80	4.626%	$105.463	$105.46	$105.45	$105.50
Purchase #2	$60.26	9.806%	$66.1691	$66.17	$66.15	$66.20
Purchase #3	$61.65	13.870%	$70.2009	$70.20	$70.20	$70.20
Purchase #4	$45.95	9.834%	$50.4687	$50.47	$50.45	$50.50
Purchase #5	$130.90	6.492%	$139.398	$139.40	$139.40	$139.40
Purchase #6	$227.62	13.587%	$258.5467	$258.55	$258.55	$258.50
Purchase #7	$168.95	3.560%	$174.9646	$174.96	$174.95	$175.00
7 purchase totals =	$796.13		$865.2110	$865.21	$865.15	$865.30