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	$214.43	10.419%	$236.7715	$236.77	$236.75	$236.80
Purchase #2	$177.31	5.605%	$187.2482	$187.25	$187.25	$187.20
Purchase #3	$23.87	7.254%	$25.6015	$25.60	$25.60	$25.60
Purchase #4	$42.27	7.646%	$45.502	$45.50	$45.50	$45.50
Purchase #5	$169.55	5.808%	$179.3975	$179.40	$179.40	$179.40
Purchase #6	$34.42	10.732%	$38.114	$38.11	$38.10	$38.10
Purchase #7	$50.85	3.416%	$52.587	$52.59	$52.60	$52.60
7 purchase totals =	$712.70		$765.2217	$765.22	$765.20	$765.20