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	$112.83	12.730%	$127.1933	$127.19	$127.20	$127.20
Purchase #2	$209.72	11.208%	$233.2254	$233.23	$233.25	$233.20
Purchase #3	$153.65	12.601%	$173.0114	$173.01	$173.00	$173.00
Purchase #4	$106.56	4.358%	$111.2039	$111.20	$111.20	$111.20
Purchase #5	$176.85	4.588%	$184.9639	$184.96	$184.95	$185.00
Purchase #6	$21.88	7.770%	$23.5801	$23.58	$23.60	$23.60
Purchase #7	$205.85	9.197%	$224.782	$224.78	$224.80	$224.80
7 purchase totals =	$987.34		$1,077.9600	$1,077.95	$1,078.00	$1,078.00