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	$248.83	4.332%	$259.6093	$259.61	$259.60	$259.60
Purchase #2	$85.76	11.300%	$95.4509	$95.45	$95.45	$95.50
Purchase #3	$206.85	4.579%	$216.3217	$216.32	$216.30	$216.30
Purchase #4	$193.50	8.334%	$209.6263	$209.63	$209.65	$209.60
Purchase #5	$41.30	9.699%	$45.3057	$45.31	$45.30	$45.30
Purchase #6	$34.77	13.215%	$39.3649	$39.36	$39.35	$39.40
Purchase #7	$196.45	4.510%	$205.3099	$205.31	$205.30	$205.30
7 purchase totals =	$1,007.46		$1,070.9887	$1,070.99	$1,070.95	$1,071.00