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	$93.81	8.298%	$101.5944	$101.59	$101.60	$101.60
Purchase #2	$200.46	9.408%	$219.3193	$219.32	$219.30	$219.30
Purchase #3	$142.41	11.290%	$158.4881	$158.49	$158.50	$158.50
Purchase #4	$83.79	8.260%	$90.7111	$90.71	$90.70	$90.70
Purchase #5	$66.72	10.634%	$73.815	$73.82	$73.80	$73.80
Purchase #6	$137.82	11.469%	$153.6266	$153.63	$153.65	$153.60
Purchase #7	$62.52	11.585%	$69.7629	$69.76	$69.75	$69.80
7 purchase totals =	$787.53		$867.3174	$867.32	$867.30	$867.30