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	$187.44	12.798%	$211.4286	$211.43	$211.45	$211.40
Purchase #2	$90.45	13.479%	$102.6418	$102.64	$102.65	$102.60
Purchase #3	$176.27	9.544%	$193.0932	$193.09	$193.10	$193.10
Purchase #4	$95.27	5.326%	$100.3441	$100.34	$100.35	$100.30
Purchase #5	$225.31	7.220%	$241.5774	$241.58	$241.60	$241.60
Purchase #6	$129.72	3.690%	$134.5067	$134.51	$134.50	$134.50
Purchase #7	$37.72	7.820%	$40.6697	$40.67	$40.65	$40.70
7 purchase totals =	$942.18		$1,024.2615	$1,024.26	$1,024.30	$1,024.20