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	$124.70	12.861%	$140.7377	$140.74	$140.75	$140.70
Purchase #2	$147.64	13.795%	$168.0069	$168.01	$168.00	$168.00
Purchase #3	$37.49	3.720%	$38.8846	$38.88	$38.90	$38.90
Purchase #4	$91.32	10.515%	$100.9223	$100.92	$100.90	$100.90
Purchase #5	$167.28	13.131%	$189.2455	$189.25	$189.25	$189.20
Purchase #6	$47.35	5.667%	$50.0333	$50.03	$50.05	$50.00
Purchase #7	$127.84	7.668%	$137.6428	$137.64	$137.65	$137.60
7 purchase totals =	$743.62		$825.4731	$825.47	$825.50	$825.30