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	$140.27	4.576%	$146.6888	$146.69	$146.70	$146.70
Purchase #2	$223.37	7.382%	$239.8592	$239.86	$239.85	$239.90
Purchase #3	$51.74	5.425%	$54.5469	$54.55	$54.55	$54.50
Purchase #4	$11.98	9.149%	$13.0761	$13.08	$13.10	$13.10
Purchase #5	$45.61	13.870%	$51.9361	$51.94	$51.95	$51.90
Purchase #6	$89.85	11.119%	$99.8404	$99.84	$99.85	$99.80
Purchase #7	$172.69	6.265%	$183.509	$183.51	$183.50	$183.50
7 purchase totals =	$735.51		$789.4565	$789.47	$789.50	$789.40