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	$49.30	4.593%	$51.5643	$51.56	$51.55	$51.60
Purchase #2	$12.28	10.735%	$13.5983	$13.60	$13.60	$13.60
Purchase #3	$111.52	7.208%	$119.5584	$119.56	$119.55	$119.60
Purchase #4	$26.88	5.754%	$28.4267	$28.43	$28.45	$28.40
Purchase #5	$231.85	13.575%	$263.3236	$263.32	$263.30	$263.30
Purchase #6	$164.25	6.119%	$174.3005	$174.30	$174.30	$174.30
Purchase #7	$232.51	10.264%	$256.3748	$256.37	$256.35	$256.40
7 purchase totals =	$828.59		$907.1466	$907.14	$907.10	$907.20