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	$53.41	7.482%	$57.4061	$57.41	$57.40	$57.40
Purchase #2	$66.25	8.781%	$72.0674	$72.07	$72.05	$72.10
Purchase #3	$172.31	4.695%	$180.4	$180.40	$180.40	$180.40
Purchase #4	$180.38	13.500%	$204.7313	$204.73	$204.75	$204.70
Purchase #5	$10.42	11.314%	$11.5989	$11.60	$11.60	$11.60
Purchase #6	$145.84	11.671%	$162.861	$162.86	$162.85	$162.90
Purchase #7	$138.33	3.295%	$142.888	$142.89	$142.90	$142.90
7 purchase totals =	$766.94		$831.9527	$831.96	$831.95	$832.00