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	$158.75	8.832%	$172.7708	$172.77	$172.75	$172.80
Purchase #2	$88.75	7.493%	$95.4	$95.40	$95.40	$95.40
Purchase #3	$183.43	7.363%	$196.936	$196.94	$196.95	$196.90
Purchase #4	$22.91	12.831%	$25.8496	$25.85	$25.85	$25.80
Purchase #5	$145.88	5.165%	$153.4147	$153.41	$153.40	$153.40
Purchase #6	$133.89	4.421%	$139.8093	$139.81	$139.80	$139.80
Purchase #7	$112.27	12.561%	$126.3722	$126.37	$126.35	$126.40
7 purchase totals =	$845.88		$910.5526	$910.55	$910.50	$910.50