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	$126.39	13.205%	$143.0798	$143.08	$143.10	$143.10
Purchase #2	$48.27	6.109%	$51.2188	$51.22	$51.20	$51.20
Purchase #3	$92.99	10.628%	$102.873	$102.87	$102.85	$102.90
Purchase #4	$231.80	8.106%	$250.5897	$250.59	$250.60	$250.60
Purchase #5	$124.68	5.144%	$131.0935	$131.09	$131.10	$131.10
Purchase #6	$194.89	9.464%	$213.3344	$213.33	$213.35	$213.30
Purchase #7	$93.49	6.212%	$99.2976	$99.30	$99.30	$99.30
7 purchase totals =	$912.51		$991.4868	$991.48	$991.50	$991.50