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	$165.38	7.858%	$178.3756	$178.38	$178.40	$178.40
Purchase #2	$31.72	11.695%	$35.4297	$35.43	$35.45	$35.40
Purchase #3	$120.32	10.281%	$132.6901	$132.69	$132.70	$132.70
Purchase #4	$28.52	12.763%	$32.16	$32.16	$32.15	$32.20
Purchase #5	$16.92	6.382%	$17.9998	$18.00	$18.00	$18.00
Purchase #6	$129.46	6.176%	$137.4554	$137.46	$137.45	$137.50
Purchase #7	$161.34	10.813%	$178.7857	$178.79	$178.80	$178.80
7 purchase totals =	$653.66		$712.8963	$712.91	$712.95	$713.00