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	$78.51	4.792%	$82.2722	$82.27	$82.25	$82.30
Purchase #2	$198.82	8.406%	$215.5328	$215.53	$215.55	$215.50
Purchase #3	$134.54	12.580%	$151.4651	$151.47	$151.45	$151.50
Purchase #4	$186.37	11.684%	$208.1455	$208.15	$208.15	$208.10
Purchase #5	$207.61	7.748%	$223.6956	$223.70	$223.70	$223.70
Purchase #6	$94.65	7.830%	$102.0611	$102.06	$102.05	$102.10
Purchase #7	$112.93	7.767%	$121.7013	$121.70	$121.70	$121.70
7 purchase totals =	$1,013.43		$1,104.8736	$1,104.88	$1,104.85	$1,104.90