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	$233.46	10.213%	$257.3033	$257.30	$257.30	$257.30
Purchase #2	$178.79	9.659%	$196.0593	$196.06	$196.05	$196.10
Purchase #3	$50.45	6.350%	$53.6536	$53.65	$53.65	$53.70
Purchase #4	$171.90	11.509%	$191.684	$191.68	$191.70	$191.70
Purchase #5	$66.90	10.704%	$74.061	$74.06	$74.05	$74.10
Purchase #6	$160.66	13.731%	$182.7202	$182.72	$182.70	$182.70
Purchase #7	$54.64	13.577%	$62.0585	$62.06	$62.05	$62.10
7 purchase totals =	$916.80		$1,017.5399	$1,017.53	$1,017.50	$1,017.70