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	$205.86	3.831%	$213.7465	$213.75	$213.75	$213.70
Purchase #2	$51.26	3.738%	$53.1761	$53.18	$53.20	$53.20
Purchase #3	$147.83	4.264%	$154.1335	$154.13	$154.15	$154.10
Purchase #4	$80.66	6.257%	$85.7069	$85.71	$85.70	$85.70
Purchase #5	$72.28	13.770%	$82.233	$82.23	$82.25	$82.20
Purchase #6	$10.35	7.587%	$11.1353	$11.14	$11.15	$11.10
Purchase #7	$49.41	10.330%	$54.5141	$54.51	$54.50	$54.50
7 purchase totals =	$617.65		$654.6454	$654.65	$654.70	$654.50