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	$154.33	6.847%	$164.897	$164.90	$164.90	$164.90
Purchase #2	$105.39	5.403%	$111.0842	$111.08	$111.10	$111.10
Purchase #3	$117.33	4.267%	$122.3365	$122.34	$122.35	$122.30
Purchase #4	$107.34	3.801%	$111.42	$111.42	$111.40	$111.40
Purchase #5	$123.60	4.471%	$129.1262	$129.13	$129.15	$129.10
Purchase #6	$236.67	10.868%	$262.3913	$262.39	$262.40	$262.40
Purchase #7	$96.81	6.474%	$103.0775	$103.08	$103.10	$103.10
7 purchase totals =	$941.47		$1,004.3327	$1,004.34	$1,004.40	$1,004.30