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	$37.95	10.328%	$41.8695	$41.87	$41.85	$41.90
Purchase #2	$44.64	8.390%	$48.3853	$48.39	$48.40	$48.40
Purchase #3	$6.84	5.836%	$7.2392	$7.24	$7.25	$7.20
Purchase #4	$32.52	3.308%	$33.5958	$33.60	$33.60	$33.60
Purchase #5	$24.92	9.618%	$27.3168	$27.32	$27.30	$27.30
Purchase #6	$57.39	6.821%	$61.3046	$61.30	$61.30	$61.30
Purchase #7	$54.67	10.734%	$60.5383	$60.54	$60.55	$60.50
7 purchase totals =	$258.93		$280.2495	$280.26	$280.25	$280.20