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	$153.60	12.477%	$172.7647	$172.76	$172.75	$172.80
Purchase #2	$139.36	6.726%	$148.7334	$148.73	$148.75	$148.70
Purchase #3	$249.50	4.677%	$261.1691	$261.17	$261.15	$261.20
Purchase #4	$19.51	7.242%	$20.9229	$20.92	$20.90	$20.90
Purchase #5	$127.48	9.509%	$139.6021	$139.60	$139.60	$139.60
Purchase #6	$198.85	3.171%	$205.1555	$205.16	$205.15	$205.20
Purchase #7	$245.62	9.223%	$268.2735	$268.27	$268.25	$268.30
7 purchase totals =	$1,133.92		$1,216.6212	$1,216.61	$1,216.55	$1,216.70