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	$182.89	5.647%	$193.2178	$193.22	$193.20	$193.20
Purchase #2	$148.33	10.610%	$164.0678	$164.07	$164.05	$164.10
Purchase #3	$127.79	7.709%	$137.6413	$137.64	$137.65	$137.60
Purchase #4	$192.86	11.651%	$215.3301	$215.33	$215.35	$215.30
Purchase #5	$117.59	8.522%	$127.611	$127.61	$127.60	$127.60
Purchase #6	$244.85	3.222%	$252.7391	$252.74	$252.75	$252.70
Purchase #7	$44.86	13.592%	$50.9574	$50.96	$50.95	$51.00
7 purchase totals =	$1,059.17		$1,141.5645	$1,141.57	$1,141.55	$1,141.50