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	$153.85	5.470%	$162.2656	$162.27	$162.25	$162.30
Purchase #2	$73.34	13.297%	$83.092	$83.09	$83.10	$83.10
Purchase #3	$25.98	13.348%	$29.4478	$29.45	$29.45	$29.40
Purchase #4	$210.32	10.139%	$231.6443	$231.64	$231.65	$231.60
Purchase #5	$114.40	11.831%	$127.9347	$127.93	$127.95	$127.90
Purchase #6	$50.96	12.443%	$57.301	$57.30	$57.30	$57.30
Purchase #7	$198.47	12.780%	$223.8345	$223.83	$223.85	$223.80
7 purchase totals =	$827.32		$915.5199	$915.51	$915.55	$915.40