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	$171.79	4.737%	$179.9277	$179.93	$179.95	$179.90
Purchase #2	$207.29	4.268%	$216.1371	$216.14	$216.15	$216.10
Purchase #3	$58.71	6.450%	$62.4968	$62.50	$62.50	$62.50
Purchase #4	$100.76	11.127%	$111.9716	$111.97	$111.95	$112.00
Purchase #5	$153.29	12.359%	$172.2351	$172.24	$172.25	$172.20
Purchase #6	$118.99	10.224%	$131.1555	$131.16	$131.15	$131.20
Purchase #7	$199.63	4.624%	$208.8609	$208.86	$208.85	$208.90
7 purchase totals =	$1,010.46		$1,082.7847	$1,082.80	$1,082.80	$1,082.80