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	$80.31	7.264%	$86.1437	$86.14	$86.15	$86.10
Purchase #2	$140.81	12.540%	$158.4676	$158.47	$158.45	$158.50
Purchase #3	$88.51	10.286%	$97.6141	$97.61	$97.60	$97.60
Purchase #4	$96.36	7.223%	$103.3201	$103.32	$103.30	$103.30
Purchase #5	$168.53	7.788%	$181.6551	$181.66	$181.65	$181.70
Purchase #6	$25.93	7.282%	$27.8182	$27.82	$27.80	$27.80
Purchase #7	$244.68	13.774%	$278.3822	$278.38	$278.40	$278.40
7 purchase totals =	$845.13		$933.4010	$933.40	$933.35	$933.40