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	$248.44	5.677%	$262.5439	$262.54	$262.55	$262.50
Purchase #2	$127.67	10.777%	$141.429	$141.43	$141.45	$141.40
Purchase #3	$111.26	8.551%	$120.7738	$120.77	$120.75	$120.80
Purchase #4	$76.34	4.112%	$79.4791	$79.48	$79.50	$79.50
Purchase #5	$67.73	7.526%	$72.8274	$72.83	$72.85	$72.80
Purchase #6	$89.68	6.553%	$95.5567	$95.56	$95.55	$95.60
Purchase #7	$32.51	12.397%	$36.5403	$36.54	$36.55	$36.50
7 purchase totals =	$753.63		$809.1502	$809.15	$809.20	$809.10