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	$205.92	7.262%	$220.8739	$220.87	$220.85	$220.90
Purchase #2	$98.33	13.650%	$111.752	$111.75	$111.75	$111.80
Purchase #3	$194.39	5.193%	$204.4847	$204.48	$204.50	$204.50
Purchase #4	$234.66	12.579%	$264.1779	$264.18	$264.20	$264.20
Purchase #5	$49.32	6.606%	$52.5781	$52.58	$52.60	$52.60
Purchase #6	$73.89	10.335%	$81.5265	$81.53	$81.55	$81.50
Purchase #7	$54.83	11.168%	$60.9534	$60.95	$60.95	$61.00
7 purchase totals =	$911.34		$996.3465	$996.34	$996.40	$996.50