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	$182.81	12.398%	$205.4748	$205.47	$205.45	$205.50
Purchase #2	$18.35	8.121%	$19.8402	$19.84	$19.85	$19.80
Purchase #3	$202.57	6.867%	$216.4805	$216.48	$216.50	$216.50
Purchase #4	$178.90	6.377%	$190.3085	$190.31	$190.30	$190.30
Purchase #5	$16.44	13.174%	$18.6058	$18.61	$18.60	$18.60
Purchase #6	$143.88	11.443%	$160.3442	$160.34	$160.35	$160.30
Purchase #7	$121.58	5.115%	$127.7988	$127.80	$127.80	$127.80
7 purchase totals =	$864.53		$938.8528	$938.85	$938.85	$938.80