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	$164.25	13.840%	$186.9822	$186.98	$187.00	$187.00
Purchase #2	$88.98	13.395%	$100.8989	$100.90	$100.90	$100.90
Purchase #3	$186.37	5.332%	$196.3072	$196.31	$196.30	$196.30
Purchase #4	$197.82	9.853%	$217.3112	$217.31	$217.30	$217.30
Purchase #5	$134.65	5.857%	$142.5365	$142.54	$142.55	$142.50
Purchase #6	$206.39	7.161%	$221.1696	$221.17	$221.15	$221.20
Purchase #7	$60.55	13.385%	$68.6546	$68.65	$68.65	$68.70
7 purchase totals =	$1,039.01		$1,133.8602	$1,133.86	$1,133.85	$1,133.90