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	$29.64	9.501%	$32.4561	$32.46	$32.45	$32.50
Purchase #2	$194.61	10.483%	$215.011	$215.01	$215.00	$215.00
Purchase #3	$154.51	11.503%	$172.2833	$172.28	$172.30	$172.30
Purchase #4	$16.46	3.680%	$17.0657	$17.07	$17.05	$17.10
Purchase #5	$130.60	13.195%	$147.8327	$147.83	$147.85	$147.80
Purchase #6	$18.91	3.810%	$19.6305	$19.63	$19.65	$19.60
Purchase #7	$161.26	12.792%	$181.8884	$181.89	$181.90	$181.90
7 purchase totals =	$705.99		$786.1677	$786.17	$786.20	$786.20