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	$126.89	8.107%	$137.177	$137.18	$137.20	$137.20
Purchase #2	$143.65	5.859%	$152.0665	$152.07	$152.05	$152.10
Purchase #3	$214.52	10.347%	$236.7164	$236.72	$236.70	$236.70
Purchase #4	$41.37	9.621%	$45.3502	$45.35	$45.35	$45.40
Purchase #5	$101.55	10.111%	$111.8177	$111.82	$111.80	$111.80
Purchase #6	$12.68	11.360%	$14.1204	$14.12	$14.10	$14.10
Purchase #7	$238.87	10.367%	$263.6337	$263.63	$263.65	$263.60
7 purchase totals =	$879.53		$960.8819	$960.89	$960.85	$960.90