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	$167.89	11.567%	$187.3098	$187.31	$187.30	$187.30
Purchase #2	$57.42	9.245%	$62.7285	$62.73	$62.75	$62.70
Purchase #3	$219.49	9.778%	$240.9517	$240.95	$240.95	$241.00
Purchase #4	$113.83	4.867%	$119.3701	$119.37	$119.35	$119.40
Purchase #5	$141.91	3.339%	$146.6484	$146.65	$146.65	$146.60
Purchase #6	$40.81	10.734%	$45.1905	$45.19	$45.20	$45.20
Purchase #7	$52.31	3.478%	$54.1293	$54.13	$54.15	$54.10
7 purchase totals =	$793.66		$856.3283	$856.33	$856.35	$856.30