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	$241.98	5.791%	$255.9931	$255.99	$256.00	$256.00
Purchase #2	$54.91	11.761%	$61.368	$61.37	$61.35	$61.40
Purchase #3	$229.96	12.709%	$259.1856	$259.19	$259.20	$259.20
Purchase #4	$94.42	11.543%	$105.3189	$105.32	$105.30	$105.30
Purchase #5	$167.73	10.729%	$185.7258	$185.73	$185.75	$185.70
Purchase #6	$60.50	5.706%	$63.9521	$63.95	$63.95	$64.00
Purchase #7	$114.78	7.510%	$123.4	$123.40	$123.40	$123.40
7 purchase totals =	$964.28		$1,054.9435	$1,054.95	$1,054.95	$1,055.00