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	$52.38	9.161%	$57.1785	$57.18	$57.20	$57.20
Purchase #2	$94.76	5.847%	$100.3006	$100.30	$100.30	$100.30
Purchase #3	$13.77	11.601%	$15.3675	$15.37	$15.35	$15.40
Purchase #4	$49.31	12.309%	$55.3796	$55.38	$55.40	$55.40
Purchase #5	$37.85	5.545%	$39.9488	$39.95	$39.95	$39.90
Purchase #6	$167.42	5.595%	$176.7871	$176.79	$176.80	$176.80
Purchase #7	$39.29	3.286%	$40.5811	$40.58	$40.60	$40.60
7 purchase totals =	$454.78		$485.5432	$485.55	$485.60	$485.60