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	$139.25	9.459%	$152.4217	$152.42	$152.40	$152.40
Purchase #2	$94.83	13.404%	$107.541	$107.54	$107.55	$107.50
Purchase #3	$50.58	13.526%	$57.4215	$57.42	$57.40	$57.40
Purchase #4	$221.95	12.664%	$250.0577	$250.06	$250.05	$250.10
Purchase #5	$9.71	7.597%	$10.4477	$10.45	$10.45	$10.40
Purchase #6	$99.97	9.630%	$109.5971	$109.60	$109.60	$109.60
Purchase #7	$214.72	5.722%	$227.0063	$227.01	$227.00	$227.00
7 purchase totals =	$831.01		$914.4930	$914.50	$914.45	$914.40