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	$134.54	4.381%	$140.4342	$140.43	$140.45	$140.40
Purchase #2	$83.30	8.548%	$90.4205	$90.42	$90.40	$90.40
Purchase #3	$21.52	8.456%	$23.3397	$23.34	$23.35	$23.30
Purchase #4	$95.90	6.678%	$102.3042	$102.30	$102.30	$102.30
Purchase #5	$199.90	11.768%	$223.4242	$223.42	$223.40	$223.40
Purchase #6	$179.78	13.785%	$204.5627	$204.56	$204.55	$204.60
Purchase #7	$82.69	11.850%	$92.4888	$92.49	$92.50	$92.50
7 purchase totals =	$797.63		$876.9743	$876.96	$876.95	$876.90