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	$107.34	10.806%	$118.9392	$118.94	$118.95	$118.90
Purchase #2	$91.54	12.472%	$102.9569	$102.96	$102.95	$103.00
Purchase #3	$134.43	13.257%	$152.2514	$152.25	$152.25	$152.30
Purchase #4	$213.73	10.352%	$235.8553	$235.86	$235.85	$235.90
Purchase #5	$132.57	9.874%	$145.66	$145.66	$145.65	$145.70
Purchase #6	$223.84	7.697%	$241.069	$241.07	$241.05	$241.10
Purchase #7	$18.83	13.563%	$21.3839	$21.38	$21.40	$21.40
7 purchase totals =	$922.28		$1,018.1157	$1,018.12	$1,018.10	$1,018.30