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	$95.83	5.465%	$101.0671	$101.07	$101.05	$101.10
Purchase #2	$237.59	7.707%	$255.9011	$255.90	$255.90	$255.90
Purchase #3	$30.83	3.548%	$31.9238	$31.92	$31.90	$31.90
Purchase #4	$57.52	8.708%	$62.5288	$62.53	$62.55	$62.50
Purchase #5	$245.52	4.381%	$256.2762	$256.28	$256.30	$256.30
Purchase #6	$132.61	5.536%	$139.9513	$139.95	$139.95	$140.00
Purchase #7	$115.63	12.749%	$130.3717	$130.37	$130.35	$130.40
7 purchase totals =	$915.53		$978.0200	$978.02	$978.00	$978.10