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	$104.49	11.210%	$116.2033	$116.20	$116.20	$116.20
Purchase #2	$126.91	7.612%	$136.5704	$136.57	$136.55	$136.60
Purchase #3	$23.30	3.659%	$24.1525	$24.15	$24.15	$24.20
Purchase #4	$95.57	10.682%	$105.7788	$105.78	$105.80	$105.80
Purchase #5	$43.55	6.630%	$46.4374	$46.44	$46.45	$46.40
Purchase #6	$64.49	10.436%	$71.2202	$71.22	$71.20	$71.20
Purchase #7	$62.42	13.868%	$71.0764	$71.08	$71.10	$71.10
7 purchase totals =	$520.73		$571.4390	$571.44	$571.45	$571.50