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	$214.51	12.736%	$241.83	$241.83	$241.85	$241.80
Purchase #2	$17.82	11.682%	$19.9017	$19.90	$19.90	$19.90
Purchase #3	$138.88	9.615%	$152.2333	$152.23	$152.25	$152.20
Purchase #4	$186.57	4.698%	$195.3351	$195.34	$195.35	$195.30
Purchase #5	$66.95	3.578%	$69.3455	$69.35	$69.35	$69.30
Purchase #6	$43.59	4.299%	$45.4639	$45.46	$45.45	$45.50
Purchase #7	$249.29	13.824%	$283.7518	$283.75	$283.75	$283.80
7 purchase totals =	$917.61		$1,007.8613	$1,007.86	$1,007.90	$1,007.80