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	$235.83	10.379%	$260.3068	$260.31	$260.30	$260.30
Purchase #2	$162.87	11.529%	$181.6473	$181.65	$181.65	$181.60
Purchase #3	$177.39	9.724%	$194.6394	$194.64	$194.65	$194.60
Purchase #4	$144.60	9.635%	$158.5322	$158.53	$158.55	$158.50
Purchase #5	$42.52	9.360%	$46.4999	$46.50	$46.50	$46.50
Purchase #6	$234.89	13.199%	$265.8931	$265.89	$265.90	$265.90
Purchase #7	$22.81	5.743%	$24.12	$24.12	$24.10	$24.10
7 purchase totals =	$1,020.91		$1,131.6387	$1,131.64	$1,131.65	$1,131.50