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	$41.59	4.766%	$43.5722	$43.57	$43.55	$43.60
Purchase #2	$158.54	6.741%	$169.2272	$169.23	$169.25	$169.20
Purchase #3	$131.83	8.646%	$143.228	$143.23	$143.25	$143.20
Purchase #4	$102.34	4.810%	$107.2626	$107.26	$107.25	$107.30
Purchase #5	$249.38	5.673%	$263.5273	$263.53	$263.55	$263.50
Purchase #6	$192.46	10.676%	$213.007	$213.01	$213.00	$213.00
Purchase #7	$129.57	12.489%	$145.752	$145.75	$145.75	$145.80
7 purchase totals =	$1,005.71		$1,085.5763	$1,085.58	$1,085.60	$1,085.60