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	$110.25	7.806%	$118.8561	$118.86	$118.85	$118.90
Purchase #2	$131.26	4.468%	$137.1247	$137.12	$137.10	$137.10
Purchase #3	$206.77	11.511%	$230.5713	$230.57	$230.55	$230.60
Purchase #4	$12.81	5.194%	$13.4754	$13.48	$13.50	$13.50
Purchase #5	$39.74	6.118%	$42.1713	$42.17	$42.15	$42.20
Purchase #6	$23.26	5.184%	$24.4658	$24.47	$24.45	$24.50
Purchase #7	$40.27	7.757%	$43.3937	$43.39	$43.40	$43.40
7 purchase totals =	$564.36		$610.0583	$610.06	$610.00	$610.20