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	$14.60	3.103%	$15.053	$15.05	$15.05	$15.10
Purchase #2	$222.93	7.389%	$239.4023	$239.40	$239.40	$239.40
Purchase #3	$72.87	7.284%	$78.1779	$78.18	$78.20	$78.20
Purchase #4	$91.72	9.463%	$100.3995	$100.40	$100.40	$100.40
Purchase #5	$221.73	10.528%	$245.0737	$245.07	$245.05	$245.10
Purchase #6	$15.82	6.521%	$16.8516	$16.85	$16.85	$16.90
Purchase #7	$147.87	11.131%	$164.3294	$164.33	$164.35	$164.30
7 purchase totals =	$787.54		$859.2874	$859.28	$859.30	$859.40