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	$170.62	3.303%	$176.2556	$176.26	$176.25	$176.30
Purchase #2	$146.29	8.757%	$159.1006	$159.10	$159.10	$159.10
Purchase #3	$180.45	3.365%	$186.5221	$186.52	$186.50	$186.50
Purchase #4	$194.84	6.763%	$208.017	$208.02	$208.00	$208.00
Purchase #5	$53.98	10.146%	$59.4568	$59.46	$59.45	$59.50
Purchase #6	$206.31	13.149%	$233.4377	$233.44	$233.45	$233.40
Purchase #7	$117.92	4.415%	$123.1262	$123.13	$123.15	$123.10
7 purchase totals =	$1,070.41		$1,145.9160	$1,145.93	$1,145.90	$1,145.90