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	$200.91	12.796%	$226.6184	$226.62	$226.60	$226.60
Purchase #2	$20.77	10.190%	$22.8865	$22.89	$22.90	$22.90
Purchase #3	$41.28	8.865%	$44.9395	$44.94	$44.95	$44.90
Purchase #4	$80.56	3.409%	$83.3063	$83.31	$83.30	$83.30
Purchase #5	$78.53	6.296%	$83.4742	$83.47	$83.45	$83.50
Purchase #6	$51.98	5.330%	$54.7505	$54.75	$54.75	$54.80
Purchase #7	$189.95	4.461%	$198.4237	$198.42	$198.40	$198.40
7 purchase totals =	$663.98		$714.3991	$714.40	$714.35	$714.40