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	$204.56	11.228%	$227.528	$227.53	$227.55	$227.50
Purchase #2	$224.56	11.342%	$250.0296	$250.03	$250.05	$250.00
Purchase #3	$86.87	13.845%	$98.8972	$98.90	$98.90	$98.90
Purchase #4	$77.25	4.229%	$80.5169	$80.52	$80.50	$80.50
Purchase #5	$46.42	13.789%	$52.8209	$52.82	$52.80	$52.80
Purchase #6	$214.69	10.524%	$237.284	$237.28	$237.30	$237.30
Purchase #7	$153.81	12.276%	$172.6917	$172.69	$172.70	$172.70
7 purchase totals =	$1,008.16		$1,119.7683	$1,119.77	$1,119.80	$1,119.70