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	$210.77	7.768%	$227.1426	$227.14	$227.15	$227.10
Purchase #2	$154.57	8.443%	$167.6203	$167.62	$167.60	$167.60
Purchase #3	$78.53	10.673%	$86.9115	$86.91	$86.90	$86.90
Purchase #4	$164.84	9.482%	$180.4701	$180.47	$180.45	$180.50
Purchase #5	$99.65	12.487%	$112.0933	$112.09	$112.10	$112.10
Purchase #6	$48.53	3.328%	$50.1451	$50.15	$50.15	$50.10
Purchase #7	$118.58	11.114%	$131.759	$131.76	$131.75	$131.80
7 purchase totals =	$875.47		$956.1419	$956.14	$956.10	$956.10