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	$176.87	7.661%	$190.42	$190.42	$190.40	$190.40
Purchase #2	$48.28	10.339%	$53.2717	$53.27	$53.25	$53.30
Purchase #3	$118.62	7.191%	$127.15	$127.15	$127.15	$127.20
Purchase #4	$148.61	3.229%	$153.4086	$153.41	$153.40	$153.40
Purchase #5	$193.77	5.214%	$203.8732	$203.87	$203.85	$203.90
Purchase #6	$150.55	5.619%	$159.0094	$159.01	$159.00	$159.00
Purchase #7	$138.93	12.500%	$156.2963	$156.30	$156.30	$156.30
7 purchase totals =	$975.63		$1,043.4292	$1,043.43	$1,043.35	$1,043.50