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	$214.27	10.184%	$236.0913	$236.09	$236.10	$236.10
Purchase #2	$180.45	7.241%	$193.5164	$193.52	$193.50	$193.50
Purchase #3	$96.50	8.680%	$104.8762	$104.88	$104.90	$104.90
Purchase #4	$140.52	8.850%	$152.956	$152.96	$152.95	$153.00
Purchase #5	$236.47	5.384%	$249.2015	$249.20	$249.20	$249.20
Purchase #6	$39.82	6.677%	$42.4788	$42.48	$42.50	$42.50
Purchase #7	$37.52	7.852%	$40.4661	$40.47	$40.45	$40.50
7 purchase totals =	$945.55		$1,019.5863	$1,019.60	$1,019.60	$1,019.70