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	$144.50	13.103%	$163.4338	$163.43	$163.45	$163.40
Purchase #2	$152.57	13.670%	$173.4263	$173.43	$173.45	$173.40
Purchase #3	$199.32	8.117%	$215.4988	$215.50	$215.50	$215.50
Purchase #4	$190.83	5.228%	$200.8066	$200.81	$200.80	$200.80
Purchase #5	$208.71	3.676%	$216.3822	$216.38	$216.40	$216.40
Purchase #6	$191.59	4.104%	$199.4529	$199.45	$199.45	$199.50
Purchase #7	$111.64	7.869%	$120.425	$120.43	$120.45	$120.40
7 purchase totals =	$1,199.16		$1,289.4256	$1,289.43	$1,289.50	$1,289.40