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	$172.67	11.709%	$192.8879	$192.89	$192.90	$192.90
Purchase #2	$162.47	5.760%	$171.8283	$171.83	$171.85	$171.80
Purchase #3	$41.83	11.622%	$46.6915	$46.69	$46.70	$46.70
Purchase #4	$86.54	10.735%	$95.8301	$95.83	$95.85	$95.80
Purchase #5	$190.49	9.134%	$207.8894	$207.89	$207.90	$207.90
Purchase #6	$223.51	3.306%	$230.8992	$230.90	$230.90	$230.90
Purchase #7	$187.26	9.381%	$204.8269	$204.83	$204.85	$204.80
7 purchase totals =	$1,064.77		$1,150.8533	$1,150.86	$1,150.95	$1,150.80