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	$64.51	8.435%	$69.9514	$69.95	$69.95	$70.00
Purchase #2	$160.72	6.440%	$171.0704	$171.07	$171.05	$171.10
Purchase #3	$127.42	13.714%	$144.8944	$144.89	$144.90	$144.90
Purchase #4	$95.65	8.564%	$103.8415	$103.84	$103.85	$103.80
Purchase #5	$184.28	3.335%	$190.4257	$190.43	$190.45	$190.40
Purchase #6	$118.98	7.678%	$128.1153	$128.12	$128.10	$128.10
Purchase #7	$248.74	3.587%	$257.6623	$257.66	$257.65	$257.70
7 purchase totals =	$1,000.30		$1,065.9610	$1,065.96	$1,065.95	$1,066.00