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	$160.38	6.134%	$170.2177	$170.22	$170.20	$170.20
Purchase #2	$185.55	4.462%	$193.8292	$193.83	$193.85	$193.80
Purchase #3	$231.93	12.842%	$261.7145	$261.71	$261.70	$261.70
Purchase #4	$78.55	5.171%	$82.6118	$82.61	$82.60	$82.60
Purchase #5	$93.25	11.422%	$103.901	$103.90	$103.90	$103.90
Purchase #6	$158.39	12.601%	$178.3487	$178.35	$178.35	$178.30
Purchase #7	$145.66	6.731%	$155.4644	$155.46	$155.45	$155.50
7 purchase totals =	$1,053.71		$1,146.0873	$1,146.08	$1,146.05	$1,146.00