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	$33.42	10.743%	$37.0103	$37.01	$37.00	$37.00
Purchase #2	$74.51	11.451%	$83.0421	$83.04	$83.05	$83.00
Purchase #3	$128.90	13.558%	$146.3763	$146.38	$146.40	$146.40
Purchase #4	$51.26	7.834%	$55.2757	$55.28	$55.30	$55.30
Purchase #5	$102.25	4.815%	$107.1733	$107.17	$107.15	$107.20
Purchase #6	$153.26	8.244%	$165.8948	$165.89	$165.90	$165.90
Purchase #7	$33.40	11.550%	$37.2577	$37.26	$37.25	$37.30
7 purchase totals =	$577.00		$632.0302	$632.03	$632.05	$632.10