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	$46.49	12.677%	$52.3835	$52.38	$52.40	$52.40
Purchase #2	$115.58	3.668%	$119.8195	$119.82	$119.80	$119.80
Purchase #3	$213.98	5.376%	$225.4836	$225.48	$225.50	$225.50
Purchase #4	$107.90	3.330%	$111.4931	$111.49	$111.50	$111.50
Purchase #5	$167.66	6.687%	$178.8714	$178.87	$178.85	$178.90
Purchase #6	$35.92	13.804%	$40.8784	$40.88	$40.90	$40.90
Purchase #7	$207.87	9.311%	$227.2248	$227.22	$227.20	$227.20
7 purchase totals =	$895.40		$956.1543	$956.14	$956.15	$956.20