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	$95.29	10.422%	$105.2211	$105.22	$105.20	$105.20
Purchase #2	$33.56	5.437%	$35.3847	$35.38	$35.40	$35.40
Purchase #3	$34.83	5.114%	$36.6112	$36.61	$36.60	$36.60
Purchase #4	$159.40	3.488%	$164.9599	$164.96	$164.95	$165.00
Purchase #5	$243.75	7.733%	$262.5992	$262.60	$262.60	$262.60
Purchase #6	$72.76	3.855%	$75.5649	$75.56	$75.55	$75.60
Purchase #7	$43.26	13.606%	$49.146	$49.15	$49.15	$49.10
7 purchase totals =	$682.85		$729.4870	$729.48	$729.45	$729.50