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	$69.80	3.740%	$72.4105	$72.41	$72.40	$72.40
Purchase #2	$53.29	11.714%	$59.5324	$59.53	$59.55	$59.50
Purchase #3	$64.83	13.143%	$73.3506	$73.35	$73.35	$73.40
Purchase #4	$49.25	13.309%	$55.8047	$55.80	$55.80	$55.80
Purchase #5	$99.95	12.189%	$112.1329	$112.13	$112.15	$112.10
Purchase #6	$172.60	11.825%	$193.01	$193.01	$193.00	$193.00
Purchase #7	$46.45	7.782%	$50.0647	$50.06	$50.05	$50.10
7 purchase totals =	$556.17		$616.3058	$616.29	$616.30	$616.30