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	$94.43	9.641%	$103.534	$103.53	$103.55	$103.50
Purchase #2	$226.57	6.426%	$241.1294	$241.13	$241.15	$241.10
Purchase #3	$136.38	12.835%	$153.8844	$153.88	$153.90	$153.90
Purchase #4	$132.86	13.125%	$150.2979	$150.30	$150.30	$150.30
Purchase #5	$116.56	13.743%	$132.5788	$132.58	$132.60	$132.60
Purchase #6	$21.64	4.434%	$22.5995	$22.60	$22.60	$22.60
Purchase #7	$43.97	6.644%	$46.8914	$46.89	$46.90	$46.90
7 purchase totals =	$772.41		$850.9154	$850.91	$851.00	$850.90