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	$236.59	13.348%	$268.17	$268.17	$268.15	$268.20
Purchase #2	$59.55	9.293%	$65.084	$65.08	$65.10	$65.10
Purchase #3	$204.93	6.245%	$217.7279	$217.73	$217.75	$217.70
Purchase #4	$11.69	7.194%	$12.531	$12.53	$12.55	$12.50
Purchase #5	$31.38	10.335%	$34.6231	$34.62	$34.60	$34.60
Purchase #6	$65.38	3.249%	$67.5042	$67.50	$67.50	$67.50
Purchase #7	$147.31	10.191%	$162.3224	$162.32	$162.30	$162.30
7 purchase totals =	$756.83		$827.9626	$827.95	$827.95	$827.90