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	$217.94	13.811%	$248.0397	$248.04	$248.05	$248.00
Purchase #2	$74.94	7.246%	$80.3702	$80.37	$80.35	$80.40
Purchase #3	$162.34	8.729%	$176.5107	$176.51	$176.50	$176.50
Purchase #4	$131.77	7.401%	$141.5223	$141.52	$141.50	$141.50
Purchase #5	$71.86	9.318%	$78.5559	$78.56	$78.55	$78.60
Purchase #6	$182.86	13.776%	$208.0508	$208.05	$208.05	$208.10
Purchase #7	$160.98	12.837%	$181.645	$181.65	$181.65	$181.60
7 purchase totals =	$1,002.69		$1,114.6946	$1,114.70	$1,114.65	$1,114.70