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	$189.65	11.154%	$210.8036	$210.80	$210.80	$210.80
Purchase #2	$183.81	12.208%	$206.2495	$206.25	$206.25	$206.20
Purchase #3	$56.45	5.770%	$59.7072	$59.71	$59.70	$59.70
Purchase #4	$193.58	13.332%	$219.3881	$219.39	$219.40	$219.40
Purchase #5	$113.60	12.169%	$127.424	$127.42	$127.40	$127.40
Purchase #6	$80.64	3.442%	$83.4156	$83.42	$83.40	$83.40
Purchase #7	$131.68	3.674%	$136.5179	$136.52	$136.50	$136.50
7 purchase totals =	$949.41		$1,043.5059	$1,043.51	$1,043.45	$1,043.40