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	$66.37	7.796%	$71.5442	$71.54	$71.55	$71.50
Purchase #2	$62.34	8.146%	$67.4182	$67.42	$67.40	$67.40
Purchase #3	$12.93	7.416%	$13.8889	$13.89	$13.90	$13.90
Purchase #4	$118.54	13.383%	$134.4042	$134.40	$134.40	$134.40
Purchase #5	$183.60	7.211%	$196.8394	$196.84	$196.85	$196.80
Purchase #6	$101.53	8.344%	$110.0017	$110.00	$110.00	$110.00
Purchase #7	$226.54	7.730%	$244.0515	$244.05	$244.05	$244.10
7 purchase totals =	$771.85		$838.1481	$838.14	$838.15	$838.10