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	$210.59	8.545%	$228.5849	$228.58	$228.60	$228.60
Purchase #2	$194.98	11.500%	$217.4027	$217.40	$217.40	$217.40
Purchase #3	$25.27	9.167%	$27.5865	$27.59	$27.60	$27.60
Purchase #4	$137.92	3.396%	$142.6038	$142.60	$142.60	$142.60
Purchase #5	$110.76	3.390%	$114.5148	$114.51	$114.50	$114.50
Purchase #6	$203.65	7.444%	$218.8097	$218.81	$218.80	$218.80
Purchase #7	$39.59	8.723%	$43.0434	$43.04	$43.05	$43.00
7 purchase totals =	$922.76		$992.5458	$992.53	$992.55	$992.50