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	$32.80	10.380%	$36.2046	$36.20	$36.20	$36.20
Purchase #2	$118.72	7.516%	$127.643	$127.64	$127.65	$127.60
Purchase #3	$70.55	3.357%	$72.9184	$72.92	$72.90	$72.90
Purchase #4	$121.67	12.389%	$136.7437	$136.74	$136.75	$136.70
Purchase #5	$108.63	13.745%	$123.5612	$123.56	$123.55	$123.60
Purchase #6	$241.86	12.505%	$272.1046	$272.10	$272.10	$272.10
Purchase #7	$214.25	13.584%	$243.3537	$243.35	$243.35	$243.40
7 purchase totals =	$908.48		$1,012.5292	$1,012.51	$1,012.50	$1,012.50