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	$248.68	3.726%	$257.9458	$257.95	$257.95	$257.90
Purchase #2	$107.59	4.669%	$112.6134	$112.61	$112.60	$112.60
Purchase #3	$83.53	7.171%	$89.5199	$89.52	$89.50	$89.50
Purchase #4	$56.72	9.504%	$62.1107	$62.11	$62.10	$62.10
Purchase #5	$200.29	12.787%	$225.9011	$225.90	$225.90	$225.90
Purchase #6	$43.99	10.184%	$48.4699	$48.47	$48.45	$48.50
Purchase #7	$236.25	6.231%	$250.9707	$250.97	$250.95	$251.00
7 purchase totals =	$977.05		$1,047.5315	$1,047.53	$1,047.45	$1,047.50