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	$145.36	5.375%	$153.1731	$153.17	$153.15	$153.20
Purchase #2	$13.40	10.711%	$14.8353	$14.84	$14.85	$14.80
Purchase #3	$131.87	13.379%	$149.5129	$149.51	$149.50	$149.50
Purchase #4	$153.57	12.302%	$172.4622	$172.46	$172.45	$172.50
Purchase #5	$236.49	9.424%	$258.7768	$258.78	$258.80	$258.80
Purchase #6	$159.89	11.493%	$178.2662	$178.27	$178.25	$178.30
Purchase #7	$55.31	13.584%	$62.8233	$62.82	$62.80	$62.80
7 purchase totals =	$895.89		$989.8498	$989.85	$989.80	$989.90