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	$45.77	6.821%	$48.892	$48.89	$48.90	$48.90
Purchase #2	$14.25	4.323%	$14.866	$14.87	$14.85	$14.90
Purchase #3	$40.65	4.242%	$42.3744	$42.37	$42.35	$42.40
Purchase #4	$171.58	6.317%	$182.4187	$182.42	$182.40	$182.40
Purchase #5	$156.73	3.452%	$162.1403	$162.14	$162.15	$162.10
Purchase #6	$34.98	8.670%	$38.0128	$38.01	$38.00	$38.00
Purchase #7	$112.30	3.429%	$116.1508	$116.15	$116.15	$116.20
7 purchase totals =	$576.26		$604.8550	$604.85	$604.80	$604.90