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	$67.51	4.685%	$70.6728	$70.67	$70.65	$70.70
Purchase #2	$154.48	11.871%	$172.8183	$172.82	$172.80	$172.80
Purchase #3	$191.68	3.366%	$198.1319	$198.13	$198.15	$198.10
Purchase #4	$75.60	4.296%	$78.8478	$78.85	$78.85	$78.80
Purchase #5	$41.93	10.613%	$46.38	$46.38	$46.40	$46.40
Purchase #6	$108.30	8.178%	$117.1568	$117.16	$117.15	$117.20
Purchase #7	$36.95	3.813%	$38.3589	$38.36	$38.35	$38.40
7 purchase totals =	$676.45		$722.3665	$722.37	$722.35	$722.40