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	$38.30	13.488%	$43.4659	$43.47	$43.45	$43.50
Purchase #2	$56.63	4.544%	$59.2033	$59.20	$59.20	$59.20
Purchase #3	$130.51	11.221%	$145.1545	$145.15	$145.15	$145.20
Purchase #4	$27.47	3.472%	$28.4238	$28.42	$28.40	$28.40
Purchase #5	$42.32	11.297%	$47.1009	$47.10	$47.10	$47.10
Purchase #6	$139.83	5.551%	$147.592	$147.59	$147.60	$147.60
Purchase #7	$48.88	10.371%	$53.9493	$53.95	$53.95	$53.90
7 purchase totals =	$483.94		$524.8897	$524.88	$524.85	$524.90