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	$69.59	12.345%	$78.1809	$78.18	$78.20	$78.20
Purchase #2	$49.89	8.707%	$54.2339	$54.23	$54.25	$54.20
Purchase #3	$28.37	10.559%	$31.3656	$31.37	$31.35	$31.40
Purchase #4	$11.89	4.722%	$12.4514	$12.45	$12.45	$12.50
Purchase #5	$111.33	12.812%	$125.5936	$125.59	$125.60	$125.60
Purchase #6	$40.79	3.643%	$42.276	$42.28	$42.30	$42.30
Purchase #7	$48.58	6.194%	$51.589	$51.59	$51.60	$51.60
7 purchase totals =	$360.44		$395.6904	$395.69	$395.75	$395.80