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	$114.30	11.647%	$127.6125	$127.61	$127.60	$127.60
Purchase #2	$58.42	13.521%	$66.319	$66.32	$66.30	$66.30
Purchase #3	$198.64	13.525%	$225.5061	$225.51	$225.50	$225.50
Purchase #4	$153.96	11.236%	$171.2589	$171.26	$171.25	$171.30
Purchase #5	$94.82	7.286%	$101.7286	$101.73	$101.75	$101.70
Purchase #6	$162.47	13.870%	$185.0046	$185.00	$185.00	$185.00
Purchase #7	$117.27	5.111%	$123.2637	$123.26	$123.25	$123.30
7 purchase totals =	$899.88		$1,000.6934	$1,000.69	$1,000.65	$1,000.70