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	$114.26	5.500%	$120.5443	$120.54	$120.55	$120.50
Purchase #2	$207.58	3.269%	$214.3658	$214.37	$214.35	$214.40
Purchase #3	$67.31	4.766%	$70.518	$70.52	$70.50	$70.50
Purchase #4	$149.94	7.337%	$160.9411	$160.94	$160.95	$160.90
Purchase #5	$194.96	10.318%	$215.076	$215.08	$215.10	$215.10
Purchase #6	$94.54	11.675%	$105.5775	$105.58	$105.60	$105.60
Purchase #7	$208.34	4.689%	$218.1091	$218.11	$218.10	$218.10
7 purchase totals =	$1,036.93		$1,105.1318	$1,105.14	$1,105.15	$1,105.10