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	$143.59	7.325%	$154.108	$154.11	$154.10	$154.10
Purchase #2	$169.68	13.390%	$192.4002	$192.40	$192.40	$192.40
Purchase #3	$141.93	6.701%	$151.4407	$151.44	$151.45	$151.40
Purchase #4	$78.47	6.107%	$83.2622	$83.26	$83.25	$83.30
Purchase #5	$88.95	12.511%	$100.0785	$100.08	$100.10	$100.10
Purchase #6	$110.31	5.174%	$116.0174	$116.02	$116.00	$116.00
Purchase #7	$102.81	8.659%	$111.7123	$111.71	$111.70	$111.70
7 purchase totals =	$835.74		$909.0193	$909.02	$909.00	$909.00