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	$150.67	4.401%	$157.301	$157.30	$157.30	$157.30
Purchase #2	$17.98	4.104%	$18.7179	$18.72	$18.70	$18.70
Purchase #3	$82.37	5.612%	$86.9926	$86.99	$87.00	$87.00
Purchase #4	$56.93	4.271%	$59.3615	$59.36	$59.35	$59.40
Purchase #5	$103.35	9.163%	$112.82	$112.82	$112.80	$112.80
Purchase #6	$61.31	13.187%	$69.3949	$69.39	$69.40	$69.40
Purchase #7	$248.97	12.390%	$279.8174	$279.82	$279.80	$279.80
7 purchase totals =	$721.58		$784.4053	$784.40	$784.35	$784.40