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	$140.74	7.388%	$151.1379	$151.14	$151.15	$151.10
Purchase #2	$215.71	13.857%	$245.6009	$245.60	$245.60	$245.60
Purchase #3	$46.58	10.416%	$51.4318	$51.43	$51.45	$51.40
Purchase #4	$89.59	5.339%	$94.3732	$94.37	$94.35	$94.40
Purchase #5	$35.53	12.563%	$39.9936	$39.99	$40.00	$40.00
Purchase #6	$118.94	10.501%	$131.4299	$131.43	$131.45	$131.40
Purchase #7	$107.73	4.644%	$112.733	$112.73	$112.75	$112.70
7 purchase totals =	$754.82		$826.7003	$826.69	$826.75	$826.60