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	$116.62	10.291%	$128.6214	$128.62	$128.60	$128.60
Purchase #2	$217.53	11.439%	$242.4133	$242.41	$242.40	$242.40
Purchase #3	$99.77	9.327%	$109.0755	$109.08	$109.10	$109.10
Purchase #4	$13.39	6.795%	$14.2999	$14.30	$14.30	$14.30
Purchase #5	$250.78	10.872%	$278.0448	$278.04	$278.05	$278.00
Purchase #6	$44.73	10.321%	$49.3466	$49.35	$49.35	$49.30
Purchase #7	$69.94	3.820%	$72.6117	$72.61	$72.60	$72.60
7 purchase totals =	$812.76		$894.4132	$894.41	$894.40	$894.30