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	$151.60	10.353%	$167.2951	$167.30	$167.30	$167.30
Purchase #2	$19.70	8.508%	$21.3761	$21.38	$21.40	$21.40
Purchase #3	$41.45	13.245%	$46.9401	$46.94	$46.95	$46.90
Purchase #4	$165.60	9.847%	$181.9066	$181.91	$181.90	$181.90
Purchase #5	$181.96	7.247%	$195.1466	$195.15	$195.15	$195.10
Purchase #6	$188.25	4.328%	$196.3975	$196.40	$196.40	$196.40
Purchase #7	$55.45	6.430%	$59.0154	$59.02	$59.00	$59.00
7 purchase totals =	$804.01		$868.0774	$868.10	$868.10	$868.00