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	$147.39	9.521%	$161.423	$161.42	$161.40	$161.40
Purchase #2	$178.38	4.163%	$185.806	$185.81	$185.80	$185.80
Purchase #3	$117.69	7.836%	$126.9122	$126.91	$126.90	$126.90
Purchase #4	$140.25	11.733%	$156.7055	$156.71	$156.70	$156.70
Purchase #5	$125.45	7.111%	$134.3707	$134.37	$134.35	$134.40
Purchase #6	$38.34	10.512%	$42.3703	$42.37	$42.35	$42.40
Purchase #7	$242.98	8.461%	$263.5385	$263.54	$263.55	$263.50
7 purchase totals =	$990.48		$1,071.1262	$1,071.13	$1,071.05	$1,071.10