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	$94.41	5.689%	$99.781	$99.78	$99.80	$99.80
Purchase #2	$160.39	4.163%	$167.067	$167.07	$167.05	$167.10
Purchase #3	$98.87	8.718%	$107.4895	$107.49	$107.50	$107.50
Purchase #4	$156.97	10.543%	$173.5193	$173.52	$173.50	$173.50
Purchase #5	$177.26	10.866%	$196.5211	$196.52	$196.50	$196.50
Purchase #6	$118.94	6.785%	$127.0101	$127.01	$127.00	$127.00
Purchase #7	$76.69	4.125%	$79.8535	$79.85	$79.85	$79.90
7 purchase totals =	$883.53		$951.2415	$951.24	$951.20	$951.30