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	$209.82	7.276%	$225.0865	$225.09	$225.10	$225.10
Purchase #2	$103.83	8.295%	$112.4427	$112.44	$112.45	$112.40
Purchase #3	$217.88	10.259%	$240.2323	$240.23	$240.25	$240.20
Purchase #4	$209.49	10.694%	$231.8929	$231.89	$231.90	$231.90
Purchase #5	$9.59	7.123%	$10.2731	$10.27	$10.25	$10.30
Purchase #6	$127.59	4.525%	$133.3634	$133.36	$133.35	$133.40
Purchase #7	$84.25	8.145%	$91.1122	$91.11	$91.10	$91.10
7 purchase totals =	$962.45		$1,044.4031	$1,044.39	$1,044.40	$1,044.40