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	$176.94	13.210%	$200.3138	$200.31	$200.30	$200.30
Purchase #2	$83.48	7.228%	$89.5139	$89.51	$89.50	$89.50
Purchase #3	$207.92	11.521%	$231.8745	$231.87	$231.85	$231.90
Purchase #4	$141.49	13.815%	$161.0368	$161.04	$161.05	$161.00
Purchase #5	$123.31	5.563%	$130.1697	$130.17	$130.15	$130.20
Purchase #6	$191.94	8.483%	$208.2223	$208.22	$208.20	$208.20
Purchase #7	$100.93	11.429%	$112.4653	$112.47	$112.45	$112.50
7 purchase totals =	$1,026.01		$1,133.5963	$1,133.59	$1,133.50	$1,133.60