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	$101.98	6.456%	$108.5638	$108.56	$108.55	$108.60
Purchase #2	$105.40	11.390%	$117.4051	$117.41	$117.40	$117.40
Purchase #3	$31.31	12.153%	$35.1151	$35.12	$35.10	$35.10
Purchase #4	$112.78	9.412%	$123.3949	$123.39	$123.40	$123.40
Purchase #5	$184.61	6.379%	$196.3863	$196.39	$196.40	$196.40
Purchase #6	$223.40	7.733%	$240.6755	$240.68	$240.70	$240.70
Purchase #7	$194.56	10.396%	$214.7865	$214.79	$214.80	$214.80
7 purchase totals =	$954.04		$1,036.3272	$1,036.34	$1,036.35	$1,036.40