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	$137.32	8.675%	$149.2325	$149.23	$149.25	$149.20
Purchase #2	$139.58	5.414%	$147.1369	$147.14	$147.15	$147.10
Purchase #3	$139.63	10.497%	$154.287	$154.29	$154.30	$154.30
Purchase #4	$90.37	7.742%	$97.3664	$97.37	$97.35	$97.40
Purchase #5	$32.86	13.805%	$37.3963	$37.40	$37.40	$37.40
Purchase #6	$178.39	5.689%	$188.5386	$188.54	$188.55	$188.50
Purchase #7	$241.27	7.706%	$259.8623	$259.86	$259.85	$259.90
7 purchase totals =	$959.42		$1,033.8200	$1,033.83	$1,033.85	$1,033.80