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	$144.76	3.775%	$150.2247	$150.22	$150.20	$150.20
Purchase #2	$246.32	11.393%	$274.3832	$274.38	$274.40	$274.40
Purchase #3	$14.85	3.706%	$15.4003	$15.40	$15.40	$15.40
Purchase #4	$129.60	5.233%	$136.382	$136.38	$136.40	$136.40
Purchase #5	$84.43	3.654%	$87.5151	$87.52	$87.50	$87.50
Purchase #6	$241.95	9.387%	$264.6618	$264.66	$264.65	$264.70
Purchase #7	$139.37	12.443%	$156.7118	$156.71	$156.70	$156.70
7 purchase totals =	$1,001.28		$1,085.2789	$1,085.27	$1,085.25	$1,085.30