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	$107.90	5.318%	$113.6381	$113.64	$113.65	$113.60
Purchase #2	$155.60	12.495%	$175.0422	$175.04	$175.05	$175.00
Purchase #3	$151.82	4.166%	$158.1448	$158.14	$158.15	$158.10
Purchase #4	$110.99	11.504%	$123.7583	$123.76	$123.75	$123.80
Purchase #5	$9.88	9.632%	$10.8316	$10.83	$10.85	$10.80
Purchase #6	$196.67	13.626%	$223.4683	$223.47	$223.45	$223.50
Purchase #7	$238.63	8.223%	$258.2525	$258.25	$258.25	$258.30
7 purchase totals =	$971.49		$1,063.1358	$1,063.13	$1,063.15	$1,063.10