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	$103.78	5.511%	$109.4993	$109.50	$109.50	$109.50
Purchase #2	$29.54	11.699%	$32.9959	$33.00	$33.00	$33.00
Purchase #3	$113.33	12.671%	$127.69	$127.69	$127.70	$127.70
Purchase #4	$122.62	8.694%	$133.2806	$133.28	$133.30	$133.30
Purchase #5	$156.83	13.851%	$178.5525	$178.55	$178.55	$178.60
Purchase #6	$179.65	9.341%	$196.4311	$196.43	$196.45	$196.40
Purchase #7	$155.42	4.234%	$162.0005	$162.00	$162.00	$162.00
7 purchase totals =	$861.17		$940.4499	$940.45	$940.50	$940.50