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	$34.69	7.113%	$37.1575	$37.16	$37.15	$37.20
Purchase #2	$33.87	13.329%	$38.3845	$38.38	$38.40	$38.40
Purchase #3	$143.68	13.349%	$162.8598	$162.86	$162.85	$162.90
Purchase #4	$231.60	11.324%	$257.8264	$257.83	$257.85	$257.80
Purchase #5	$67.31	3.284%	$69.5205	$69.52	$69.50	$69.50
Purchase #6	$54.77	12.465%	$61.5971	$61.60	$61.60	$61.60
Purchase #7	$81.60	6.127%	$86.5996	$86.60	$86.60	$86.60
7 purchase totals =	$647.52		$713.9454	$713.95	$713.95	$714.00