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	$90.33	7.452%	$97.0614	$97.06	$97.05	$97.10
Purchase #2	$16.86	4.325%	$17.5892	$17.59	$17.60	$17.60
Purchase #3	$109.30	11.578%	$121.9548	$121.95	$121.95	$122.00
Purchase #4	$12.31	12.698%	$13.8731	$13.87	$13.85	$13.90
Purchase #5	$81.76	13.117%	$92.4845	$92.48	$92.50	$92.50
Purchase #6	$38.44	11.601%	$42.8994	$42.90	$42.90	$42.90
Purchase #7	$107.72	5.544%	$113.692	$113.69	$113.70	$113.70
7 purchase totals =	$456.72		$499.5544	$499.54	$499.55	$499.70