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	$146.29	4.272%	$152.5395	$152.54	$152.55	$152.50
Purchase #2	$176.42	8.867%	$192.0632	$192.06	$192.05	$192.10
Purchase #3	$172.76	13.480%	$196.048	$196.05	$196.05	$196.00
Purchase #4	$228.83	11.598%	$255.3697	$255.37	$255.35	$255.40
Purchase #5	$10.25	9.861%	$11.2608	$11.26	$11.25	$11.30
Purchase #6	$169.41	7.605%	$182.2936	$182.29	$182.30	$182.30
Purchase #7	$131.74	9.363%	$144.0748	$144.07	$144.05	$144.10
7 purchase totals =	$1,035.70		$1,133.6496	$1,133.64	$1,133.60	$1,133.70