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	$220.28	12.180%	$247.1101	$247.11	$247.10	$247.10
Purchase #2	$97.45	7.707%	$104.9605	$104.96	$104.95	$105.00
Purchase #3	$69.37	5.766%	$73.3699	$73.37	$73.35	$73.40
Purchase #4	$50.47	6.773%	$53.8883	$53.89	$53.90	$53.90
Purchase #5	$20.81	3.407%	$21.519	$21.52	$21.50	$21.50
Purchase #6	$63.43	12.560%	$71.3968	$71.40	$71.40	$71.40
Purchase #7	$38.85	11.681%	$43.3881	$43.39	$43.40	$43.40
7 purchase totals =	$560.66		$615.6327	$615.64	$615.60	$615.70