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	$162.88	13.825%	$185.3982	$185.40	$185.40	$185.40
Purchase #2	$83.98	5.496%	$88.5955	$88.60	$88.60	$88.60
Purchase #3	$53.68	6.850%	$57.3571	$57.36	$57.35	$57.40
Purchase #4	$78.66	3.618%	$81.5059	$81.51	$81.50	$81.50
Purchase #5	$143.29	12.228%	$160.8115	$160.81	$160.80	$160.80
Purchase #6	$6.93	7.292%	$7.4353	$7.44	$7.45	$7.40
Purchase #7	$41.61	10.855%	$46.1268	$46.13	$46.15	$46.10
7 purchase totals =	$571.03		$627.2303	$627.25	$627.25	$627.20