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	$106.99	9.262%	$116.8994	$116.90	$116.90	$116.90
Purchase #2	$217.28	4.597%	$227.2684	$227.27	$227.25	$227.30
Purchase #3	$165.83	6.411%	$176.4614	$176.46	$176.45	$176.50
Purchase #4	$146.53	12.793%	$165.2756	$165.28	$165.30	$165.30
Purchase #5	$140.77	9.350%	$153.932	$153.93	$153.95	$153.90
Purchase #6	$46.29	13.529%	$52.5526	$52.55	$52.55	$52.60
Purchase #7	$131.37	11.286%	$146.1964	$146.20	$146.20	$146.20
7 purchase totals =	$955.06		$1,038.5858	$1,038.59	$1,038.60	$1,038.70