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	$58.61	12.312%	$65.8261	$65.83	$65.85	$65.80
Purchase #2	$85.41	12.197%	$95.8275	$95.83	$95.85	$95.80
Purchase #3	$123.30	5.771%	$130.4156	$130.42	$130.40	$130.40
Purchase #4	$175.72	6.492%	$187.1277	$187.13	$187.15	$187.10
Purchase #5	$247.42	4.109%	$257.5865	$257.59	$257.60	$257.60
Purchase #6	$29.96	11.225%	$33.323	$33.32	$33.30	$33.30
Purchase #7	$85.61	5.325%	$90.1687	$90.17	$90.15	$90.20
7 purchase totals =	$806.03		$860.2751	$860.29	$860.30	$860.20