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	$228.81	13.483%	$259.6605	$259.66	$259.65	$259.70
Purchase #2	$211.42	12.290%	$237.4035	$237.40	$237.40	$237.40
Purchase #3	$147.78	4.555%	$154.5114	$154.51	$154.50	$154.50
Purchase #4	$240.96	7.213%	$258.3404	$258.34	$258.35	$258.30
Purchase #5	$137.78	5.297%	$145.0782	$145.08	$145.10	$145.10
Purchase #6	$92.83	7.109%	$99.4293	$99.43	$99.45	$99.40
Purchase #7	$219.81	13.637%	$249.7855	$249.79	$249.80	$249.80
7 purchase totals =	$1,279.39		$1,404.2088	$1,404.21	$1,404.25	$1,404.20