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	$126.89	7.509%	$136.4182	$136.42	$136.40	$136.40
Purchase #2	$51.59	5.795%	$54.5796	$54.58	$54.60	$54.60
Purchase #3	$202.62	11.288%	$225.4917	$225.49	$225.50	$225.50
Purchase #4	$119.49	10.187%	$131.6624	$131.66	$131.65	$131.70
Purchase #5	$196.37	10.205%	$216.4096	$216.41	$216.40	$216.40
Purchase #6	$156.28	5.317%	$164.5894	$164.59	$164.60	$164.60
Purchase #7	$243.29	5.282%	$256.1406	$256.14	$256.15	$256.10
7 purchase totals =	$1,096.53		$1,185.2915	$1,185.29	$1,185.30	$1,185.30