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	$53.80	10.126%	$59.2478	$59.25	$59.25	$59.20
Purchase #2	$127.97	10.567%	$141.4926	$141.49	$141.50	$141.50
Purchase #3	$64.47	11.814%	$72.0865	$72.09	$72.10	$72.10
Purchase #4	$169.99	4.345%	$177.3761	$177.38	$177.40	$177.40
Purchase #5	$17.36	10.326%	$19.1526	$19.15	$19.15	$19.20
Purchase #6	$240.72	9.464%	$263.5017	$263.50	$263.50	$263.50
Purchase #7	$133.93	10.217%	$147.6136	$147.61	$147.60	$147.60
7 purchase totals =	$808.24		$880.4709	$880.47	$880.50	$880.50