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	$175.26	8.658%	$190.434	$190.43	$190.45	$190.40
Purchase #2	$96.27	7.105%	$103.11	$103.11	$103.10	$103.10
Purchase #3	$91.56	6.823%	$97.8071	$97.81	$97.80	$97.80
Purchase #4	$180.73	11.175%	$200.9266	$200.93	$200.95	$200.90
Purchase #5	$18.44	3.814%	$19.1433	$19.14	$19.15	$19.10
Purchase #6	$187.73	4.712%	$196.5758	$196.58	$196.60	$196.60
Purchase #7	$167.52	5.463%	$176.6716	$176.67	$176.65	$176.70
7 purchase totals =	$917.51		$984.6684	$984.67	$984.70	$984.60