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	$142.94	10.195%	$157.5127	$157.51	$157.50	$157.50
Purchase #2	$153.26	7.598%	$164.9047	$164.90	$164.90	$164.90
Purchase #3	$140.31	7.194%	$150.4039	$150.40	$150.40	$150.40
Purchase #4	$185.89	10.460%	$205.3341	$205.33	$205.35	$205.30
Purchase #5	$113.27	9.169%	$123.6557	$123.66	$123.65	$123.70
Purchase #6	$121.33	13.419%	$137.6113	$137.61	$137.60	$137.60
Purchase #7	$66.50	9.354%	$72.7204	$72.72	$72.70	$72.70
7 purchase totals =	$923.50		$1,012.1428	$1,012.13	$1,012.10	$1,012.10