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	$53.90	4.388%	$56.2651	$56.27	$56.25	$56.30
Purchase #2	$13.53	5.348%	$14.2536	$14.25	$14.25	$14.30
Purchase #3	$175.64	12.690%	$197.9287	$197.93	$197.95	$197.90
Purchase #4	$127.61	13.631%	$145.0045	$145.00	$145.00	$145.00
Purchase #5	$234.86	12.622%	$264.504	$264.50	$264.50	$264.50
Purchase #6	$80.59	3.649%	$83.5307	$83.53	$83.55	$83.50
Purchase #7	$113.75	12.504%	$127.9733	$127.97	$127.95	$128.00
7 purchase totals =	$799.88		$889.4599	$889.45	$889.45	$889.50