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	$235.62	8.407%	$255.4286	$255.43	$255.45	$255.40
Purchase #2	$176.71	13.131%	$199.9138	$199.91	$199.90	$199.90
Purchase #3	$88.90	12.387%	$99.912	$99.91	$99.90	$99.90
Purchase #4	$53.85	12.338%	$60.494	$60.49	$60.50	$60.50
Purchase #5	$200.96	13.527%	$228.1439	$228.14	$228.15	$228.10
Purchase #6	$224.36	7.640%	$241.5011	$241.50	$241.50	$241.50
Purchase #7	$139.68	11.409%	$155.6161	$155.62	$155.60	$155.60
7 purchase totals =	$1,120.08		$1,241.0095	$1,241.00	$1,241.00	$1,240.90