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	$137.75	11.575%	$153.6946	$153.69	$153.70	$153.70
Purchase #2	$179.44	9.285%	$196.101	$196.10	$196.10	$196.10
Purchase #3	$47.97	3.166%	$49.4887	$49.49	$49.50	$49.50
Purchase #4	$92.48	10.576%	$102.2607	$102.26	$102.25	$102.30
Purchase #5	$108.68	7.117%	$116.4148	$116.41	$116.40	$116.40
Purchase #6	$195.25	10.514%	$215.7786	$215.78	$215.80	$215.80
Purchase #7	$133.70	8.112%	$144.5457	$144.55	$144.55	$144.50
7 purchase totals =	$895.27		$978.2841	$978.28	$978.30	$978.30