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	$42.26	4.732%	$44.2597	$44.26	$44.25	$44.30
Purchase #2	$99.44	9.544%	$108.9306	$108.93	$108.95	$108.90
Purchase #3	$102.71	4.547%	$107.3802	$107.38	$107.40	$107.40
Purchase #4	$78.39	5.373%	$82.6019	$82.60	$82.60	$82.60
Purchase #5	$67.78	6.243%	$72.0115	$72.01	$72.00	$72.00
Purchase #6	$93.56	13.182%	$105.8931	$105.89	$105.90	$105.90
Purchase #7	$14.68	10.138%	$16.1683	$16.17	$16.15	$16.20
7 purchase totals =	$498.82		$537.2453	$537.24	$537.25	$537.30