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	$148.32	12.757%	$167.2412	$167.24	$167.25	$167.20
Purchase #2	$113.97	7.382%	$122.3833	$122.38	$122.40	$122.40
Purchase #3	$242.58	12.297%	$272.4101	$272.41	$272.40	$272.40
Purchase #4	$206.68	8.868%	$225.0084	$225.01	$225.00	$225.00
Purchase #5	$73.39	7.552%	$78.9324	$78.93	$78.95	$78.90
Purchase #6	$118.64	8.687%	$128.9463	$128.95	$128.95	$128.90
Purchase #7	$87.37	3.469%	$90.4009	$90.40	$90.40	$90.40
7 purchase totals =	$990.95		$1,085.3226	$1,085.32	$1,085.35	$1,085.20