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	$67.38	8.834%	$73.3323	$73.33	$73.35	$73.30
Purchase #2	$17.70	13.728%	$20.1299	$20.13	$20.15	$20.10
Purchase #3	$185.95	10.745%	$205.9303	$205.93	$205.95	$205.90
Purchase #4	$123.81	6.844%	$132.2836	$132.28	$132.30	$132.30
Purchase #5	$109.30	8.178%	$118.2386	$118.24	$118.25	$118.20
Purchase #6	$203.59	10.675%	$225.3232	$225.32	$225.30	$225.30
Purchase #7	$99.39	13.205%	$112.5144	$112.51	$112.50	$112.50
7 purchase totals =	$807.12		$887.7523	$887.74	$887.80	$887.60