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	$231.47	10.776%	$256.4132	$256.41	$256.40	$256.40
Purchase #2	$48.52	10.854%	$53.7864	$53.79	$53.80	$53.80
Purchase #3	$225.33	9.830%	$247.4799	$247.48	$247.50	$247.50
Purchase #4	$171.96	5.334%	$181.1323	$181.13	$181.15	$181.10
Purchase #5	$75.86	3.247%	$78.3232	$78.32	$78.30	$78.30
Purchase #6	$222.90	13.485%	$252.9581	$252.96	$252.95	$253.00
Purchase #7	$204.86	11.407%	$228.2284	$228.23	$228.25	$228.20
7 purchase totals =	$1,180.90		$1,298.3215	$1,298.32	$1,298.35	$1,298.30