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	$133.38	7.189%	$142.9687	$142.97	$142.95	$143.00
Purchase #2	$128.38	12.649%	$144.6188	$144.62	$144.60	$144.60
Purchase #3	$89.44	12.658%	$100.7613	$100.76	$100.75	$100.80
Purchase #4	$231.83	5.155%	$243.7808	$243.78	$243.80	$243.80
Purchase #5	$34.69	9.154%	$37.8655	$37.87	$37.85	$37.90
Purchase #6	$185.51	12.461%	$208.6264	$208.63	$208.65	$208.60
Purchase #7	$192.51	7.719%	$207.3698	$207.37	$207.35	$207.40
7 purchase totals =	$995.74		$1,085.9913	$1,086.00	$1,085.95	$1,086.10