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	$219.90	3.725%	$228.0913	$228.09	$228.10	$228.10
Purchase #2	$140.50	9.671%	$154.0878	$154.09	$154.10	$154.10
Purchase #3	$32.52	9.592%	$35.6393	$35.64	$35.65	$35.60
Purchase #4	$103.85	7.345%	$111.4778	$111.48	$111.50	$111.50
Purchase #5	$165.69	3.702%	$171.8238	$171.82	$171.80	$171.80
Purchase #6	$133.96	7.779%	$144.3807	$144.38	$144.40	$144.40
Purchase #7	$70.85	5.741%	$74.9175	$74.92	$74.90	$74.90
7 purchase totals =	$867.27		$920.4182	$920.42	$920.45	$920.40