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	$200.70	11.757%	$224.2963	$224.30	$224.30	$224.30
Purchase #2	$165.82	13.458%	$188.1361	$188.14	$188.15	$188.10
Purchase #3	$113.67	4.564%	$118.8579	$118.86	$118.85	$118.90
Purchase #4	$94.73	11.667%	$105.7821	$105.78	$105.80	$105.80
Purchase #5	$164.81	5.362%	$173.6471	$173.65	$173.65	$173.60
Purchase #6	$117.47	8.472%	$127.4221	$127.42	$127.40	$127.40
Purchase #7	$201.81	7.157%	$216.2535	$216.25	$216.25	$216.30
7 purchase totals =	$1,059.01		$1,154.3951	$1,154.40	$1,154.40	$1,154.40