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	$58.94	4.357%	$61.508	$61.51	$61.50	$61.50
Purchase #2	$231.88	6.456%	$246.8502	$246.85	$246.85	$246.90
Purchase #3	$144.30	8.511%	$156.5814	$156.58	$156.60	$156.60
Purchase #4	$55.40	11.213%	$61.612	$61.61	$61.60	$61.60
Purchase #5	$56.54	13.667%	$64.2673	$64.27	$64.25	$64.30
Purchase #6	$238.98	7.335%	$256.5092	$256.51	$256.50	$256.50
Purchase #7	$142.98	4.834%	$149.8917	$149.89	$149.90	$149.90
7 purchase totals =	$929.02		$997.2198	$997.22	$997.20	$997.30