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	$105.91	5.345%	$111.5709	$111.57	$111.55	$111.60
Purchase #2	$208.30	9.745%	$228.5988	$228.60	$228.60	$228.60
Purchase #3	$46.47	12.619%	$52.334	$52.33	$52.35	$52.30
Purchase #4	$137.87	3.824%	$143.1421	$143.14	$143.15	$143.10
Purchase #5	$111.73	5.359%	$117.7176	$117.72	$117.70	$117.70
Purchase #6	$171.90	4.537%	$179.6991	$179.70	$179.70	$179.70
Purchase #7	$137.43	8.581%	$149.2229	$149.22	$149.20	$149.20
7 purchase totals =	$919.61		$982.2854	$982.28	$982.25	$982.20