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	$120.74	9.737%	$132.4965	$132.50	$132.50	$132.50
Purchase #2	$123.71	5.733%	$130.8023	$130.80	$130.80	$130.80
Purchase #3	$238.83	13.147%	$270.229	$270.23	$270.25	$270.20
Purchase #4	$236.91	9.447%	$259.2909	$259.29	$259.30	$259.30
Purchase #5	$141.49	3.209%	$146.0304	$146.03	$146.05	$146.00
Purchase #6	$152.61	5.804%	$161.4675	$161.47	$161.45	$161.50
Purchase #7	$39.94	6.424%	$42.5057	$42.51	$42.50	$42.50
7 purchase totals =	$1,054.23		$1,142.8223	$1,142.83	$1,142.85	$1,142.80