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	$14.75	4.210%	$15.371	$15.37	$15.35	$15.40
Purchase #2	$85.38	5.588%	$90.151	$90.15	$90.15	$90.20
Purchase #3	$78.42	6.324%	$83.3793	$83.38	$83.40	$83.40
Purchase #4	$65.28	9.559%	$71.5201	$71.52	$71.50	$71.50
Purchase #5	$158.98	9.620%	$174.2739	$174.27	$174.25	$174.30
Purchase #6	$125.84	11.119%	$139.8321	$139.83	$139.85	$139.80
Purchase #7	$68.61	8.754%	$74.6161	$74.62	$74.60	$74.60
7 purchase totals =	$597.26		$649.1435	$649.14	$649.10	$649.20