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	$138.96	9.746%	$152.503	$152.50	$152.50	$152.50
Purchase #2	$99.85	11.394%	$111.2269	$111.23	$111.25	$111.20
Purchase #3	$228.53	11.133%	$253.9722	$253.97	$253.95	$254.00
Purchase #4	$116.75	11.459%	$130.1284	$130.13	$130.15	$130.10
Purchase #5	$190.86	7.194%	$204.5905	$204.59	$204.60	$204.60
Purchase #6	$128.44	4.301%	$133.9642	$133.96	$133.95	$134.00
Purchase #7	$157.85	8.511%	$171.2846	$171.28	$171.30	$171.30
7 purchase totals =	$1,061.24		$1,157.6698	$1,157.66	$1,157.70	$1,157.70