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	$12.46	3.183%	$12.8566	$12.86	$12.85	$12.90
Purchase #2	$94.55	5.472%	$99.7238	$99.72	$99.70	$99.70
Purchase #3	$244.51	7.871%	$263.7554	$263.76	$263.75	$263.80
Purchase #4	$241.73	5.513%	$255.0566	$255.06	$255.05	$255.10
Purchase #5	$37.77	10.129%	$41.5957	$41.60	$41.60	$41.60
Purchase #6	$130.94	4.784%	$137.2042	$137.20	$137.20	$137.20
Purchase #7	$160.42	6.453%	$170.7719	$170.77	$170.75	$170.80
7 purchase totals =	$922.38		$980.9642	$980.97	$980.90	$981.10