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	$127.85	7.255%	$137.1255	$137.13	$137.15	$137.10
Purchase #2	$157.34	3.106%	$162.227	$162.23	$162.25	$162.20
Purchase #3	$164.36	4.863%	$172.3528	$172.35	$172.35	$172.40
Purchase #4	$56.26	10.552%	$62.1966	$62.20	$62.20	$62.20
Purchase #5	$97.63	6.518%	$103.9935	$103.99	$104.00	$104.00
Purchase #6	$30.27	10.539%	$33.4602	$33.46	$33.45	$33.50
Purchase #7	$86.51	4.667%	$90.5474	$90.55	$90.55	$90.50
7 purchase totals =	$720.22		$761.9030	$761.91	$761.95	$761.90