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	$65.88	4.105%	$68.5844	$68.58	$68.60	$68.60
Purchase #2	$43.46	4.864%	$45.5739	$45.57	$45.55	$45.60
Purchase #3	$173.50	3.683%	$179.89	$179.89	$179.90	$179.90
Purchase #4	$138.83	9.376%	$151.8467	$151.85	$151.85	$151.80
Purchase #5	$100.28	8.148%	$108.4508	$108.45	$108.45	$108.50
Purchase #6	$168.69	5.644%	$178.2109	$178.21	$178.20	$178.20
Purchase #7	$156.54	9.753%	$171.8073	$171.81	$171.80	$171.80
7 purchase totals =	$847.18		$904.3640	$904.36	$904.35	$904.40