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	$161.38	11.481%	$179.908	$179.91	$179.90	$179.90
Purchase #2	$216.39	10.253%	$238.5765	$238.58	$238.60	$238.60
Purchase #3	$159.73	10.541%	$176.5671	$176.57	$176.55	$176.60
Purchase #4	$189.39	12.868%	$213.7607	$213.76	$213.75	$213.80
Purchase #5	$234.37	13.207%	$265.3232	$265.32	$265.30	$265.30
Purchase #6	$151.52	4.841%	$158.8551	$158.86	$158.85	$158.90
Purchase #7	$165.28	4.233%	$172.2763	$172.28	$172.30	$172.30
7 purchase totals =	$1,278.06		$1,405.2669	$1,405.28	$1,405.25	$1,405.40