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	$49.63	7.376%	$53.2907	$53.29	$53.30	$53.30
Purchase #2	$182.32	4.670%	$190.8343	$190.83	$190.85	$190.80
Purchase #3	$47.27	4.726%	$49.504	$49.50	$49.50	$49.50
Purchase #4	$78.69	6.355%	$83.6907	$83.69	$83.70	$83.70
Purchase #5	$107.49	5.697%	$113.6137	$113.61	$113.60	$113.60
Purchase #6	$30.52	12.400%	$34.3045	$34.30	$34.30	$34.30
Purchase #7	$174.79	7.433%	$187.7821	$187.78	$187.80	$187.80
7 purchase totals =	$670.71		$713.0200	$713.00	$713.05	$713.00