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	$164.34	6.716%	$175.3771	$175.38	$175.40	$175.40
Purchase #2	$137.90	10.440%	$152.2968	$152.30	$152.30	$152.30
Purchase #3	$141.77	11.868%	$158.5953	$158.60	$158.60	$158.60
Purchase #4	$156.59	9.110%	$170.8553	$170.86	$170.85	$170.90
Purchase #5	$17.68	4.685%	$18.5083	$18.51	$18.50	$18.50
Purchase #6	$87.32	4.235%	$91.018	$91.02	$91.00	$91.00
Purchase #7	$213.62	5.558%	$225.493	$225.49	$225.50	$225.50
7 purchase totals =	$919.22		$992.1438	$992.16	$992.15	$992.20