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	$90.43	6.680%	$96.4707	$96.47	$96.45	$96.50
Purchase #2	$134.33	6.843%	$143.5222	$143.52	$143.50	$143.50
Purchase #3	$66.71	6.179%	$70.832	$70.83	$70.85	$70.80
Purchase #4	$20.83	3.540%	$21.5674	$21.57	$21.55	$21.60
Purchase #5	$206.57	12.598%	$232.5937	$232.59	$232.60	$232.60
Purchase #6	$118.69	3.759%	$123.1516	$123.15	$123.15	$123.20
Purchase #7	$160.97	8.268%	$174.279	$174.28	$174.30	$174.30
7 purchase totals =	$798.53		$862.4166	$862.41	$862.40	$862.50