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	$103.96	7.549%	$111.8079	$111.81	$111.80	$111.80
Purchase #2	$165.32	13.412%	$187.4927	$187.49	$187.50	$187.50
Purchase #3	$79.34	11.535%	$88.4919	$88.49	$88.50	$88.50
Purchase #4	$89.91	9.454%	$98.4101	$98.41	$98.40	$98.40
Purchase #5	$224.51	9.754%	$246.4087	$246.41	$246.40	$246.40
Purchase #6	$160.49	12.249%	$180.1484	$180.15	$180.15	$180.10
Purchase #7	$241.40	7.466%	$259.4229	$259.42	$259.40	$259.40
7 purchase totals =	$1,064.93		$1,172.1826	$1,172.18	$1,172.15	$1,172.10