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	$33.59	3.720%	$34.8395	$34.84	$34.85	$34.80
Purchase #2	$127.87	13.138%	$144.6696	$144.67	$144.65	$144.70
Purchase #3	$159.88	9.808%	$175.561	$175.56	$175.55	$175.60
Purchase #4	$192.37	12.249%	$215.9334	$215.93	$215.95	$215.90
Purchase #5	$37.56	10.296%	$41.4272	$41.43	$41.45	$41.40
Purchase #6	$61.79	7.772%	$66.5923	$66.59	$66.60	$66.60
Purchase #7	$210.47	7.123%	$225.4618	$225.46	$225.45	$225.50
7 purchase totals =	$823.53		$904.4848	$904.48	$904.50	$904.50