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	$44.33	9.606%	$48.5883	$48.59	$48.60	$48.60
Purchase #2	$133.76	6.614%	$142.6069	$142.61	$142.60	$142.60
Purchase #3	$123.68	11.666%	$138.1085	$138.11	$138.10	$138.10
Purchase #4	$170.70	4.337%	$178.1033	$178.10	$178.10	$178.10
Purchase #5	$73.92	11.597%	$82.4925	$82.49	$82.50	$82.50
Purchase #6	$13.94	13.853%	$15.8711	$15.87	$15.85	$15.90
Purchase #7	$137.71	3.299%	$142.2531	$142.25	$142.25	$142.30
7 purchase totals =	$698.04		$748.0237	$748.02	$748.00	$748.10