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	$207.54	10.246%	$228.8045	$228.80	$228.80	$228.80
Purchase #2	$243.89	7.762%	$262.8207	$262.82	$262.80	$262.80
Purchase #3	$19.52	4.833%	$20.4634	$20.46	$20.45	$20.50
Purchase #4	$30.67	4.585%	$32.0762	$32.08	$32.10	$32.10
Purchase #5	$219.57	8.549%	$238.341	$238.34	$238.35	$238.30
Purchase #6	$182.52	3.683%	$189.2422	$189.24	$189.25	$189.20
Purchase #7	$48.90	11.749%	$54.6453	$54.65	$54.65	$54.60
7 purchase totals =	$952.61		$1,026.3933	$1,026.39	$1,026.40	$1,026.30