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	$181.87	13.441%	$206.3151	$206.32	$206.30	$206.30
Purchase #2	$155.88	10.362%	$172.0323	$172.03	$172.05	$172.00
Purchase #3	$78.59	11.347%	$87.5076	$87.51	$87.50	$87.50
Purchase #4	$157.51	6.714%	$168.0852	$168.09	$168.10	$168.10
Purchase #5	$175.35	7.686%	$188.8274	$188.83	$188.85	$188.80
Purchase #6	$107.71	3.506%	$111.4863	$111.49	$111.50	$111.50
Purchase #7	$134.85	6.142%	$143.1325	$143.13	$143.15	$143.10
7 purchase totals =	$991.76		$1,077.3864	$1,077.40	$1,077.45	$1,077.30