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	$55.35	9.281%	$60.487	$60.49	$60.50	$60.50
Purchase #2	$147.83	8.444%	$160.3128	$160.31	$160.30	$160.30
Purchase #3	$155.51	6.554%	$165.7021	$165.70	$165.70	$165.70
Purchase #4	$91.60	11.357%	$102.003	$102.00	$102.00	$102.00
Purchase #5	$214.71	12.558%	$241.6733	$241.67	$241.65	$241.70
Purchase #6	$164.62	12.461%	$185.1333	$185.13	$185.15	$185.10
Purchase #7	$162.54	4.853%	$170.4281	$170.43	$170.45	$170.40
7 purchase totals =	$992.16		$1,085.7396	$1,085.73	$1,085.75	$1,085.70