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	$62.65	7.793%	$67.5323	$67.53	$67.55	$67.50
Purchase #2	$231.66	9.324%	$253.26	$253.26	$253.25	$253.30
Purchase #3	$83.90	7.413%	$90.1195	$90.12	$90.10	$90.10
Purchase #4	$131.55	11.619%	$146.8348	$146.83	$146.85	$146.80
Purchase #5	$234.89	13.491%	$266.579	$266.58	$266.60	$266.60
Purchase #6	$52.26	10.353%	$57.6705	$57.67	$57.65	$57.70
Purchase #7	$99.84	12.571%	$112.3909	$112.39	$112.40	$112.40
7 purchase totals =	$896.75		$994.3870	$994.38	$994.40	$994.40