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	$182.52	3.754%	$189.3718	$189.37	$189.35	$189.40
Purchase #2	$150.73	11.633%	$168.2644	$168.26	$168.25	$168.30
Purchase #3	$70.39	3.165%	$72.6178	$72.62	$72.60	$72.60
Purchase #4	$194.31	3.106%	$200.3453	$200.35	$200.35	$200.30
Purchase #5	$108.85	10.193%	$119.9451	$119.95	$119.95	$119.90
Purchase #6	$220.77	4.216%	$230.0777	$230.08	$230.10	$230.10
Purchase #7	$198.66	5.673%	$209.93	$209.93	$209.95	$209.90
7 purchase totals =	$1,126.23		$1,190.5521	$1,190.56	$1,190.55	$1,190.50