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	$100.40	11.482%	$111.9279	$111.93	$111.95	$111.90
Purchase #2	$221.52	7.449%	$238.021	$238.02	$238.00	$238.00
Purchase #3	$152.77	6.583%	$162.8268	$162.83	$162.85	$162.80
Purchase #4	$160.35	7.689%	$172.6793	$172.68	$172.70	$172.70
Purchase #5	$152.33	13.321%	$172.6219	$172.62	$172.60	$172.60
Purchase #6	$224.61	7.541%	$241.5478	$241.55	$241.55	$241.50
Purchase #7	$100.34	3.829%	$104.182	$104.18	$104.20	$104.20
7 purchase totals =	$1,112.32		$1,203.8067	$1,203.81	$1,203.85	$1,203.70