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	$181.32	3.509%	$187.6825	$187.68	$187.70	$187.70
Purchase #2	$33.87	11.236%	$37.6756	$37.68	$37.70	$37.70
Purchase #3	$105.86	7.229%	$113.5126	$113.51	$113.50	$113.50
Purchase #4	$242.42	5.200%	$255.0258	$255.03	$255.05	$255.00
Purchase #5	$215.98	11.828%	$241.5261	$241.53	$241.55	$241.50
Purchase #6	$113.54	12.353%	$127.5656	$127.57	$127.55	$127.60
Purchase #7	$158.42	6.183%	$168.2151	$168.22	$168.20	$168.20
7 purchase totals =	$1,051.41		$1,131.2033	$1,131.22	$1,131.25	$1,131.20