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	$185.68	4.404%	$193.8573	$193.86	$193.85	$193.90
Purchase #2	$102.83	3.681%	$106.6152	$106.62	$106.60	$106.60
Purchase #3	$31.30	9.725%	$34.3439	$34.34	$34.35	$34.30
Purchase #4	$126.86	11.104%	$140.9465	$140.95	$140.95	$140.90
Purchase #5	$101.43	10.255%	$111.8316	$111.83	$111.85	$111.80
Purchase #6	$130.91	8.153%	$141.5831	$141.58	$141.60	$141.60
Purchase #7	$176.60	13.460%	$200.3704	$200.37	$200.35	$200.40
7 purchase totals =	$855.61		$929.5480	$929.55	$929.55	$929.50