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	$219.69	8.731%	$238.8711	$238.87	$238.85	$238.90
Purchase #2	$81.66	11.257%	$90.8525	$90.85	$90.85	$90.90
Purchase #3	$143.98	5.328%	$151.6513	$151.65	$151.65	$151.70
Purchase #4	$50.40	4.716%	$52.7769	$52.78	$52.80	$52.80
Purchase #5	$87.31	13.660%	$99.2365	$99.24	$99.25	$99.20
Purchase #6	$95.54	13.744%	$108.671	$108.67	$108.65	$108.70
Purchase #7	$97.47	6.459%	$103.7656	$103.77	$103.75	$103.80
7 purchase totals =	$776.05		$845.8249	$845.83	$845.80	$846.00