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	$206.77	4.826%	$216.7487	$216.75	$216.75	$216.70
Purchase #2	$95.48	7.491%	$102.6324	$102.63	$102.65	$102.60
Purchase #3	$95.88	4.387%	$100.0863	$100.09	$100.10	$100.10
Purchase #4	$173.93	6.843%	$185.832	$185.83	$185.85	$185.80
Purchase #5	$119.77	6.528%	$127.5886	$127.59	$127.60	$127.60
Purchase #6	$243.35	7.387%	$261.3263	$261.33	$261.35	$261.30
Purchase #7	$240.58	10.814%	$266.5963	$266.60	$266.60	$266.60
7 purchase totals =	$1,175.76		$1,260.8106	$1,260.82	$1,260.90	$1,260.70