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	$76.83	11.212%	$85.4442	$85.44	$85.45	$85.40
Purchase #2	$158.49	3.772%	$164.4682	$164.47	$164.45	$164.50
Purchase #3	$20.30	10.257%	$22.3822	$22.38	$22.40	$22.40
Purchase #4	$75.60	13.375%	$85.7115	$85.71	$85.70	$85.70
Purchase #5	$224.69	9.167%	$245.2873	$245.29	$245.30	$245.30
Purchase #6	$185.93	13.715%	$211.4303	$211.43	$211.45	$211.40
Purchase #7	$97.93	3.267%	$101.1294	$101.13	$101.15	$101.10
7 purchase totals =	$839.77		$915.8531	$915.85	$915.90	$915.80