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	$204.30	8.274%	$221.2038	$221.20	$221.20	$221.20
Purchase #2	$228.90	4.376%	$238.9167	$238.92	$238.90	$238.90
Purchase #3	$126.32	9.128%	$137.8505	$137.85	$137.85	$137.90
Purchase #4	$103.86	6.217%	$110.317	$110.32	$110.30	$110.30
Purchase #5	$136.25	4.195%	$141.9657	$141.97	$141.95	$142.00
Purchase #6	$49.59	7.775%	$53.4456	$53.45	$53.45	$53.40
Purchase #7	$222.40	8.238%	$240.7213	$240.72	$240.70	$240.70
7 purchase totals =	$1,071.62		$1,144.4206	$1,144.43	$1,144.35	$1,144.40