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	$99.87	13.789%	$113.6411	$113.64	$113.65	$113.60
Purchase #2	$14.29	10.764%	$15.8282	$15.83	$15.85	$15.80
Purchase #3	$30.25	9.811%	$33.2178	$33.22	$33.20	$33.20
Purchase #4	$145.72	7.492%	$156.6373	$156.64	$156.65	$156.60
Purchase #5	$195.55	6.790%	$208.8278	$208.83	$208.85	$208.80
Purchase #6	$51.80	5.117%	$54.4506	$54.45	$54.45	$54.50
Purchase #7	$43.59	3.618%	$45.1671	$45.17	$45.15	$45.20
7 purchase totals =	$581.07		$627.7699	$627.78	$627.80	$627.70