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	$149.71	13.208%	$169.4837	$169.48	$169.50	$169.50
Purchase #2	$151.67	8.470%	$164.5164	$164.52	$164.50	$164.50
Purchase #3	$177.68	6.121%	$188.5558	$188.56	$188.55	$188.60
Purchase #4	$73.48	12.858%	$82.9281	$82.93	$82.95	$82.90
Purchase #5	$172.71	11.493%	$192.5596	$192.56	$192.55	$192.60
Purchase #6	$163.92	12.412%	$184.2658	$184.27	$184.25	$184.30
Purchase #7	$179.26	10.763%	$198.5538	$198.55	$198.55	$198.60
7 purchase totals =	$1,068.43		$1,180.8632	$1,180.87	$1,180.85	$1,181.00