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	$33.25	6.658%	$35.4638	$35.46	$35.45	$35.50
Purchase #2	$120.60	13.218%	$136.5409	$136.54	$136.55	$136.50
Purchase #3	$51.95	4.139%	$54.1002	$54.10	$54.10	$54.10
Purchase #4	$192.67	11.343%	$214.5246	$214.52	$214.50	$214.50
Purchase #5	$40.71	5.149%	$42.8062	$42.81	$42.80	$42.80
Purchase #6	$50.27	10.646%	$55.6217	$55.62	$55.60	$55.60
Purchase #7	$79.27	10.828%	$87.8534	$87.85	$87.85	$87.90
7 purchase totals =	$568.72		$626.9108	$626.90	$626.85	$626.90