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	$64.83	10.633%	$71.7234	$71.72	$71.70	$71.70
Purchase #2	$94.50	11.253%	$105.1341	$105.13	$105.15	$105.10
Purchase #3	$40.99	11.493%	$45.701	$45.70	$45.70	$45.70
Purchase #4	$16.59	13.616%	$18.8489	$18.85	$18.85	$18.80
Purchase #5	$131.65	6.867%	$140.6904	$140.69	$140.70	$140.70
Purchase #6	$127.47	3.168%	$131.5082	$131.51	$131.50	$131.50
Purchase #7	$106.35	10.852%	$117.8911	$117.89	$117.90	$117.90
7 purchase totals =	$582.38		$631.4971	$631.49	$631.50	$631.40