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	$42.95	11.610%	$47.9365	$47.94	$47.95	$47.90
Purchase #2	$62.57	3.706%	$64.8888	$64.89	$64.90	$64.90
Purchase #3	$146.95	12.632%	$165.5127	$165.51	$165.50	$165.50
Purchase #4	$159.68	5.520%	$168.4943	$168.49	$168.50	$168.50
Purchase #5	$241.62	5.783%	$255.5929	$255.59	$255.60	$255.60
Purchase #6	$27.91	13.461%	$31.667	$31.67	$31.65	$31.70
Purchase #7	$204.77	3.697%	$212.3403	$212.34	$212.35	$212.30
7 purchase totals =	$886.45		$946.4325	$946.43	$946.45	$946.40