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	$225.61	11.393%	$251.3137	$251.31	$251.30	$251.30
Purchase #2	$235.39	6.417%	$250.495	$250.50	$250.50	$250.50
Purchase #3	$173.53	7.680%	$186.8571	$186.86	$186.85	$186.90
Purchase #4	$229.31	11.462%	$255.5935	$255.59	$255.60	$255.60
Purchase #5	$212.74	7.351%	$228.3785	$228.38	$228.40	$228.40
Purchase #6	$153.27	12.357%	$172.2096	$172.21	$172.20	$172.20
Purchase #7	$10.31	13.324%	$11.6837	$11.68	$11.70	$11.70
7 purchase totals =	$1,240.16		$1,356.5311	$1,356.53	$1,356.55	$1,356.60