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	$59.66	11.572%	$66.5639	$66.56	$66.55	$66.60
Purchase #2	$225.42	7.504%	$242.3355	$242.34	$242.35	$242.30
Purchase #3	$148.56	6.610%	$158.3798	$158.38	$158.40	$158.40
Purchase #4	$207.99	6.555%	$221.6237	$221.62	$221.60	$221.60
Purchase #5	$126.34	13.370%	$143.2317	$143.23	$143.25	$143.20
Purchase #6	$59.73	7.692%	$64.3244	$64.32	$64.30	$64.30
Purchase #7	$239.25	9.436%	$261.8256	$261.83	$261.85	$261.80
7 purchase totals =	$1,066.95		$1,158.2846	$1,158.28	$1,158.30	$1,158.20