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	$144.50	4.781%	$151.4085	$151.41	$151.40	$151.40
Purchase #2	$154.69	6.242%	$164.3457	$164.35	$164.35	$164.30
Purchase #3	$199.72	12.676%	$225.0365	$225.04	$225.05	$225.00
Purchase #4	$229.60	12.730%	$258.8281	$258.83	$258.85	$258.80
Purchase #5	$19.59	9.752%	$21.5004	$21.50	$21.50	$21.50
Purchase #6	$186.49	6.527%	$198.6622	$198.66	$198.65	$198.70
Purchase #7	$218.55	5.151%	$229.8075	$229.81	$229.80	$229.80
7 purchase totals =	$1,153.14		$1,249.5889	$1,249.60	$1,249.60	$1,249.50