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	$241.61	7.652%	$260.098	$260.10	$260.10	$260.10
Purchase #2	$6.80	11.787%	$7.6015	$7.60	$7.60	$7.60
Purchase #3	$240.86	13.486%	$273.3424	$273.34	$273.35	$273.30
Purchase #4	$139.60	10.663%	$154.4855	$154.49	$154.50	$154.50
Purchase #5	$39.78	7.622%	$42.812	$42.81	$42.80	$42.80
Purchase #6	$138.79	10.654%	$153.5767	$153.58	$153.60	$153.60
Purchase #7	$37.65	10.423%	$41.5743	$41.57	$41.55	$41.60
7 purchase totals =	$845.09		$933.4904	$933.49	$933.50	$933.50