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	$65.30	5.611%	$68.964	$68.96	$68.95	$69.00
Purchase #2	$82.35	10.728%	$91.1845	$91.18	$91.20	$91.20
Purchase #3	$180.92	8.582%	$196.4466	$196.45	$196.45	$196.40
Purchase #4	$43.41	13.869%	$49.4305	$49.43	$49.45	$49.40
Purchase #5	$158.66	8.154%	$171.5971	$171.60	$171.60	$171.60
Purchase #6	$15.78	5.244%	$16.6075	$16.61	$16.60	$16.60
Purchase #7	$73.81	11.601%	$82.3727	$82.37	$82.35	$82.40
7 purchase totals =	$620.23		$676.6029	$676.60	$676.60	$676.60