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	$83.70	12.584%	$94.2328	$94.23	$94.25	$94.20
Purchase #2	$56.96	7.638%	$61.3106	$61.31	$61.30	$61.30
Purchase #3	$223.51	7.350%	$239.938	$239.94	$239.95	$239.90
Purchase #4	$228.45	12.747%	$257.5705	$257.57	$257.55	$257.60
Purchase #5	$108.43	3.178%	$111.8759	$111.88	$111.90	$111.90
Purchase #6	$14.47	7.427%	$15.5447	$15.54	$15.55	$15.50
Purchase #7	$164.82	10.497%	$182.1212	$182.12	$182.10	$182.10
7 purchase totals =	$880.34		$962.5937	$962.59	$962.60	$962.50