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	$73.42	9.518%	$80.4081	$80.41	$80.40	$80.40
Purchase #2	$51.39	4.105%	$53.4996	$53.50	$53.50	$53.50
Purchase #3	$226.33	5.496%	$238.7691	$238.77	$238.75	$238.80
Purchase #4	$250.76	12.564%	$282.2655	$282.27	$282.25	$282.30
Purchase #5	$9.35	8.490%	$10.1438	$10.14	$10.15	$10.10
Purchase #6	$87.50	13.536%	$99.344	$99.34	$99.35	$99.30
Purchase #7	$229.96	12.314%	$258.2773	$258.28	$258.30	$258.30
7 purchase totals =	$928.71		$1,022.7074	$1,022.71	$1,022.70	$1,022.70