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	$153.31	12.801%	$172.9352	$172.94	$172.95	$172.90
Purchase #2	$56.94	3.851%	$59.1328	$59.13	$59.15	$59.10
Purchase #3	$34.43	10.679%	$38.1068	$38.11	$38.10	$38.10
Purchase #4	$179.51	11.840%	$200.764	$200.76	$200.75	$200.80
Purchase #5	$92.90	4.436%	$97.021	$97.02	$97.00	$97.00
Purchase #6	$230.99	9.421%	$252.7516	$252.75	$252.75	$252.80
Purchase #7	$66.72	10.740%	$73.8857	$73.89	$73.90	$73.90
7 purchase totals =	$814.80		$894.5971	$894.60	$894.60	$894.60