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	$129.60	9.192%	$141.5128	$141.51	$141.50	$141.50
Purchase #2	$108.37	3.817%	$112.5065	$112.51	$112.50	$112.50
Purchase #3	$153.65	9.754%	$168.637	$168.64	$168.65	$168.60
Purchase #4	$62.51	11.516%	$69.7087	$69.71	$69.70	$69.70
Purchase #5	$9.60	10.603%	$10.6179	$10.62	$10.60	$10.60
Purchase #6	$112.60	4.446%	$117.6062	$117.61	$117.60	$117.60
Purchase #7	$117.73	8.376%	$127.5911	$127.59	$127.60	$127.60
7 purchase totals =	$694.06		$748.1802	$748.19	$748.15	$748.10