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	$204.72	9.714%	$224.6065	$224.61	$224.60	$224.60
Purchase #2	$132.34	9.757%	$145.2524	$145.25	$145.25	$145.30
Purchase #3	$146.64	4.681%	$153.5042	$153.50	$153.50	$153.50
Purchase #4	$129.39	13.238%	$146.5186	$146.52	$146.50	$146.50
Purchase #5	$202.26	8.690%	$219.8364	$219.84	$219.85	$219.80
Purchase #6	$140.25	9.404%	$153.4391	$153.44	$153.45	$153.40
Purchase #7	$189.29	12.288%	$212.55	$212.55	$212.55	$212.60
7 purchase totals =	$1,144.89		$1,255.7072	$1,255.71	$1,255.70	$1,255.70