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	$106.80	3.340%	$110.3671	$110.37	$110.35	$110.40
Purchase #2	$38.58	9.725%	$42.3319	$42.33	$42.35	$42.30
Purchase #3	$43.57	4.592%	$45.5707	$45.57	$45.55	$45.60
Purchase #4	$118.43	4.654%	$123.9417	$123.94	$123.95	$123.90
Purchase #5	$158.39	9.443%	$173.3468	$173.35	$173.35	$173.30
Purchase #6	$11.47	10.336%	$12.6555	$12.66	$12.65	$12.70
Purchase #7	$46.60	3.461%	$48.2128	$48.21	$48.20	$48.20
7 purchase totals =	$523.84		$556.4265	$556.43	$556.40	$556.40