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	$49.71	9.433%	$54.3991	$54.40	$54.40	$54.40
Purchase #2	$115.91	11.128%	$128.8085	$128.81	$128.80	$128.80
Purchase #3	$207.38	11.613%	$231.463	$231.46	$231.45	$231.50
Purchase #4	$81.27	13.718%	$92.4186	$92.42	$92.40	$92.40
Purchase #5	$40.28	5.583%	$42.5288	$42.53	$42.55	$42.50
Purchase #6	$116.54	10.829%	$129.1601	$129.16	$129.15	$129.20
Purchase #7	$101.97	3.271%	$105.3054	$105.31	$105.30	$105.30
7 purchase totals =	$713.06		$784.0835	$784.09	$784.05	$784.10