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	$222.78	3.342%	$230.2253	$230.23	$230.25	$230.20
Purchase #2	$64.32	7.297%	$69.0134	$69.01	$69.00	$69.00
Purchase #3	$60.85	4.171%	$63.3881	$63.39	$63.40	$63.40
Purchase #4	$50.55	5.602%	$53.3818	$53.38	$53.40	$53.40
Purchase #5	$173.25	7.289%	$185.8782	$185.88	$185.90	$185.90
Purchase #6	$105.83	4.306%	$110.387	$110.39	$110.40	$110.40
Purchase #7	$170.38	4.838%	$178.623	$178.62	$178.60	$178.60
7 purchase totals =	$847.96		$890.8968	$890.90	$890.95	$890.90