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	$43.52	4.844%	$45.6281	$45.63	$45.65	$45.60
Purchase #2	$188.32	8.648%	$204.6059	$204.61	$204.60	$204.60
Purchase #3	$236.65	8.773%	$257.4113	$257.41	$257.40	$257.40
Purchase #4	$34.96	13.126%	$39.5488	$39.55	$39.55	$39.50
Purchase #5	$99.46	5.626%	$105.0556	$105.06	$105.05	$105.10
Purchase #6	$153.50	11.221%	$170.7242	$170.72	$170.70	$170.70
Purchase #7	$152.41	12.842%	$171.9825	$171.98	$172.00	$172.00
7 purchase totals =	$908.82		$994.9564	$994.96	$994.95	$994.90