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	$160.61	4.836%	$168.3771	$168.38	$168.40	$168.40
Purchase #2	$183.89	11.548%	$205.1256	$205.13	$205.15	$205.10
Purchase #3	$214.64	12.472%	$241.4099	$241.41	$241.40	$241.40
Purchase #4	$90.43	11.216%	$100.5726	$100.57	$100.55	$100.60
Purchase #5	$56.43	6.535%	$60.1177	$60.12	$60.10	$60.10
Purchase #6	$187.78	9.594%	$205.7956	$205.80	$205.80	$205.80
Purchase #7	$137.67	11.285%	$153.2061	$153.21	$153.20	$153.20
7 purchase totals =	$1,031.45		$1,134.6046	$1,134.62	$1,134.60	$1,134.60