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	$224.41	9.199%	$245.0535	$245.05	$245.05	$245.10
Purchase #2	$19.45	11.784%	$21.742	$21.74	$21.75	$21.70
Purchase #3	$75.30	4.188%	$78.4536	$78.45	$78.45	$78.50
Purchase #4	$211.30	10.312%	$233.0893	$233.09	$233.10	$233.10
Purchase #5	$72.89	11.148%	$81.0158	$81.02	$81.00	$81.00
Purchase #6	$102.35	5.546%	$108.0263	$108.03	$108.05	$108.00
Purchase #7	$17.44	9.737%	$19.1381	$19.14	$19.15	$19.10
7 purchase totals =	$723.14		$786.5186	$786.52	$786.55	$786.50