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	$176.31	5.568%	$186.1269	$186.13	$186.15	$186.10
Purchase #2	$43.67	4.111%	$45.4653	$45.47	$45.45	$45.50
Purchase #3	$76.99	12.534%	$86.6399	$86.64	$86.65	$86.60
Purchase #4	$20.34	12.683%	$22.9197	$22.92	$22.90	$22.90
Purchase #5	$29.40	8.365%	$31.8593	$31.86	$31.85	$31.90
Purchase #6	$13.91	13.370%	$15.7698	$15.77	$15.75	$15.80
Purchase #7	$38.65	3.439%	$39.9792	$39.98	$40.00	$40.00
7 purchase totals =	$399.27		$428.7601	$428.77	$428.75	$428.80