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	$163.80	5.583%	$172.945	$172.95	$172.95	$172.90
Purchase #2	$145.54	13.778%	$165.5925	$165.59	$165.60	$165.60
Purchase #3	$56.62	4.510%	$59.1736	$59.17	$59.15	$59.20
Purchase #4	$246.36	3.464%	$254.8939	$254.89	$254.90	$254.90
Purchase #5	$177.83	5.163%	$187.0114	$187.01	$187.00	$187.00
Purchase #6	$187.28	10.810%	$207.525	$207.53	$207.55	$207.50
Purchase #7	$180.81	9.594%	$198.1569	$198.16	$198.15	$198.20
7 purchase totals =	$1,158.24		$1,245.2983	$1,245.30	$1,245.30	$1,245.30