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	$228.41	4.393%	$238.4441	$238.44	$238.45	$238.40
Purchase #2	$91.27	13.826%	$103.889	$103.89	$103.90	$103.90
Purchase #3	$32.66	5.557%	$34.4749	$34.47	$34.45	$34.50
Purchase #4	$30.97	5.869%	$32.7876	$32.79	$32.80	$32.80
Purchase #5	$228.39	9.385%	$249.8244	$249.82	$249.80	$249.80
Purchase #6	$127.30	12.645%	$143.3971	$143.40	$143.40	$143.40
Purchase #7	$228.77	5.354%	$241.0183	$241.02	$241.00	$241.00
7 purchase totals =	$967.77		$1,043.8354	$1,043.83	$1,043.80	$1,043.80