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	$106.27	12.566%	$119.6239	$119.62	$119.60	$119.60
Purchase #2	$195.72	9.754%	$214.8105	$214.81	$214.80	$214.80
Purchase #3	$237.99	7.797%	$256.5461	$256.55	$256.55	$256.50
Purchase #4	$74.99	7.331%	$80.4875	$80.49	$80.50	$80.50
Purchase #5	$218.39	4.810%	$228.8946	$228.89	$228.90	$228.90
Purchase #6	$19.63	10.476%	$21.6864	$21.69	$21.70	$21.70
Purchase #7	$76.31	11.826%	$85.3344	$85.33	$85.35	$85.30
7 purchase totals =	$929.30		$1,007.3834	$1,007.38	$1,007.40	$1,007.30