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	$102.84	11.386%	$114.5494	$114.55	$114.55	$114.50
Purchase #2	$161.66	13.123%	$182.8746	$182.87	$182.85	$182.90
Purchase #3	$94.98	4.634%	$99.3814	$99.38	$99.40	$99.40
Purchase #4	$184.40	7.824%	$198.8275	$198.83	$198.85	$198.80
Purchase #5	$9.63	6.599%	$10.2655	$10.27	$10.25	$10.30
Purchase #6	$65.83	13.227%	$74.5373	$74.54	$74.55	$74.50
Purchase #7	$81.60	4.805%	$85.5209	$85.52	$85.50	$85.50
7 purchase totals =	$700.94		$765.9566	$765.96	$765.95	$765.90