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	$163.68	5.404%	$172.5253	$172.53	$172.55	$172.50
Purchase #2	$39.28	6.767%	$41.9381	$41.94	$41.95	$41.90
Purchase #3	$69.72	5.255%	$73.3838	$73.38	$73.40	$73.40
Purchase #4	$132.43	3.102%	$136.538	$136.54	$136.55	$136.50
Purchase #5	$41.43	13.274%	$46.9294	$46.93	$46.95	$46.90
Purchase #6	$105.33	11.294%	$117.226	$117.23	$117.25	$117.20
Purchase #7	$152.51	13.246%	$172.7115	$172.71	$172.70	$172.70
7 purchase totals =	$704.38		$761.2521	$761.26	$761.35	$761.10