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	$165.65	4.534%	$173.1606	$173.16	$173.15	$173.20
Purchase #2	$42.89	13.206%	$48.5541	$48.55	$48.55	$48.60
Purchase #3	$100.53	5.415%	$105.9737	$105.97	$105.95	$106.00
Purchase #4	$73.76	5.834%	$78.0632	$78.06	$78.05	$78.10
Purchase #5	$57.57	6.178%	$61.1267	$61.13	$61.15	$61.10
Purchase #6	$153.38	6.578%	$163.4693	$163.47	$163.45	$163.50
Purchase #7	$118.49	7.820%	$127.7559	$127.76	$127.75	$127.80
7 purchase totals =	$712.27		$758.1035	$758.10	$758.05	$758.30