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	$164.60	4.591%	$172.1568	$172.16	$172.15	$172.20
Purchase #2	$219.92	9.856%	$241.5953	$241.60	$241.60	$241.60
Purchase #3	$239.38	11.644%	$267.2534	$267.25	$267.25	$267.30
Purchase #4	$126.85	11.831%	$141.8576	$141.86	$141.85	$141.90
Purchase #5	$27.61	4.116%	$28.7464	$28.75	$28.75	$28.70
Purchase #6	$246.53	4.706%	$258.1317	$258.13	$258.15	$258.10
Purchase #7	$34.74	10.555%	$38.4068	$38.41	$38.40	$38.40
7 purchase totals =	$1,059.63		$1,148.1480	$1,148.16	$1,148.15	$1,148.20