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	$43.68	3.598%	$45.2516	$45.25	$45.25	$45.30
Purchase #2	$36.81	3.141%	$37.9662	$37.97	$37.95	$38.00
Purchase #3	$131.25	9.781%	$144.0876	$144.09	$144.10	$144.10
Purchase #4	$138.37	10.189%	$152.4685	$152.47	$152.45	$152.50
Purchase #5	$176.31	6.224%	$187.2835	$187.28	$187.30	$187.30
Purchase #6	$217.56	5.511%	$229.5497	$229.55	$229.55	$229.50
Purchase #7	$149.92	6.354%	$159.4459	$159.45	$159.45	$159.40
7 purchase totals =	$893.90		$956.0530	$956.06	$956.05	$956.10