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	$158.25	4.578%	$165.4947	$165.49	$165.50	$165.50
Purchase #2	$227.92	6.710%	$243.2134	$243.21	$243.20	$243.20
Purchase #3	$20.62	13.551%	$23.4142	$23.41	$23.40	$23.40
Purchase #4	$94.77	10.222%	$104.4574	$104.46	$104.45	$104.50
Purchase #5	$158.43	8.614%	$172.0772	$172.08	$172.10	$172.10
Purchase #6	$108.74	7.551%	$116.951	$116.95	$116.95	$117.00
Purchase #7	$249.90	4.156%	$260.2858	$260.29	$260.30	$260.30
7 purchase totals =	$1,018.63		$1,085.8937	$1,085.89	$1,085.90	$1,086.00