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	$173.51	13.182%	$196.3821	$196.38	$196.40	$196.40
Purchase #2	$115.41	10.691%	$127.7485	$127.75	$127.75	$127.70
Purchase #3	$13.51	12.838%	$15.2444	$15.24	$15.25	$15.20
Purchase #4	$104.47	12.216%	$117.2321	$117.23	$117.25	$117.20
Purchase #5	$90.89	11.444%	$101.2915	$101.29	$101.30	$101.30
Purchase #6	$78.83	13.130%	$89.1804	$89.18	$89.20	$89.20
Purchase #7	$237.41	12.167%	$266.2957	$266.30	$266.30	$266.30
7 purchase totals =	$814.03		$913.3747	$913.37	$913.45	$913.30