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	$216.35	5.645%	$228.563	$228.56	$228.55	$228.60
Purchase #2	$100.27	4.497%	$104.7791	$104.78	$104.80	$104.80
Purchase #3	$17.78	8.512%	$19.2934	$19.29	$19.30	$19.30
Purchase #4	$77.68	5.713%	$82.1179	$82.12	$82.10	$82.10
Purchase #5	$47.98	13.810%	$54.606	$54.61	$54.60	$54.60
Purchase #6	$16.60	12.671%	$18.7034	$18.70	$18.70	$18.70
Purchase #7	$164.37	4.732%	$172.148	$172.15	$172.15	$172.10
7 purchase totals =	$641.03		$680.2108	$680.21	$680.20	$680.20