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	$144.81	13.822%	$164.8256	$164.83	$164.85	$164.80
Purchase #2	$176.27	10.821%	$195.3442	$195.34	$195.35	$195.30
Purchase #3	$231.52	4.726%	$242.4616	$242.46	$242.45	$242.50
Purchase #4	$31.26	6.571%	$33.3141	$33.31	$33.30	$33.30
Purchase #5	$187.84	6.510%	$200.0684	$200.07	$200.05	$200.10
Purchase #6	$159.89	3.281%	$165.136	$165.14	$165.15	$165.10
Purchase #7	$232.64	9.548%	$254.8525	$254.85	$254.85	$254.90
7 purchase totals =	$1,164.23		$1,256.0024	$1,256.00	$1,256.00	$1,256.00