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	$158.75	10.322%	$175.1362	$175.14	$175.15	$175.10
Purchase #2	$87.77	13.780%	$99.8647	$99.86	$99.85	$99.90
Purchase #3	$80.60	3.369%	$83.3154	$83.32	$83.30	$83.30
Purchase #4	$198.40	8.848%	$215.9544	$215.95	$215.95	$216.00
Purchase #5	$125.78	13.826%	$143.1703	$143.17	$143.15	$143.20
Purchase #6	$59.43	3.705%	$61.6319	$61.63	$61.65	$61.60
Purchase #7	$93.83	13.417%	$106.4192	$106.42	$106.40	$106.40
7 purchase totals =	$804.56		$885.4921	$885.49	$885.45	$885.50