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	$107.34	5.130%	$112.8465	$112.85	$112.85	$112.80
Purchase #2	$52.48	4.380%	$54.7786	$54.78	$54.80	$54.80
Purchase #3	$106.93	5.390%	$112.6935	$112.69	$112.70	$112.70
Purchase #4	$77.97	13.486%	$88.485	$88.49	$88.50	$88.50
Purchase #5	$146.81	13.264%	$166.2829	$166.28	$166.30	$166.30
Purchase #6	$72.54	6.104%	$76.9678	$76.97	$76.95	$77.00
Purchase #7	$63.40	4.795%	$66.44	$66.44	$66.45	$66.40
7 purchase totals =	$627.47		$678.4943	$678.50	$678.55	$678.50