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	$43.83	4.733%	$45.9045	$45.90	$45.90	$45.90
Purchase #2	$171.39	12.320%	$192.5052	$192.51	$192.50	$192.50
Purchase #3	$213.32	4.653%	$223.2458	$223.25	$223.25	$223.20
Purchase #4	$129.95	8.473%	$140.9607	$140.96	$140.95	$141.00
Purchase #5	$16.42	10.382%	$18.1247	$18.12	$18.10	$18.10
Purchase #6	$208.81	13.288%	$236.5567	$236.56	$236.55	$236.60
Purchase #7	$75.45	13.420%	$85.5754	$85.58	$85.60	$85.60
7 purchase totals =	$859.17		$942.8730	$942.88	$942.85	$942.90