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	$208.87	7.131%	$223.7645	$223.76	$223.75	$223.80
Purchase #2	$60.92	9.205%	$66.5277	$66.53	$66.55	$66.50
Purchase #3	$93.78	10.246%	$103.3887	$103.39	$103.40	$103.40
Purchase #4	$82.70	7.751%	$89.1101	$89.11	$89.10	$89.10
Purchase #5	$214.90	10.621%	$237.7245	$237.72	$237.70	$237.70
Purchase #6	$77.36	3.776%	$80.2811	$80.28	$80.30	$80.30
Purchase #7	$167.52	4.834%	$175.6179	$175.62	$175.60	$175.60
7 purchase totals =	$906.05		$976.4145	$976.41	$976.40	$976.40