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	$79.47	8.738%	$86.4141	$86.41	$86.40	$86.40
Purchase #2	$79.78	13.832%	$90.8152	$90.82	$90.80	$90.80
Purchase #3	$149.39	3.790%	$155.0519	$155.05	$155.05	$155.10
Purchase #4	$101.43	6.753%	$108.2796	$108.28	$108.30	$108.30
Purchase #5	$137.41	12.244%	$154.2345	$154.23	$154.25	$154.20
Purchase #6	$176.94	5.457%	$186.5956	$186.60	$186.60	$186.60
Purchase #7	$164.70	12.649%	$185.5329	$185.53	$185.55	$185.50
7 purchase totals =	$889.12		$966.9238	$966.92	$966.95	$966.90