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	$206.41	3.612%	$213.8655	$213.87	$213.85	$213.90
Purchase #2	$14.53	3.281%	$15.0067	$15.01	$15.00	$15.00
Purchase #3	$75.98	8.244%	$82.2438	$82.24	$82.25	$82.20
Purchase #4	$34.30	8.561%	$37.2364	$37.24	$37.25	$37.20
Purchase #5	$145.52	13.320%	$164.9033	$164.90	$164.90	$164.90
Purchase #6	$154.36	5.531%	$162.8977	$162.90	$162.90	$162.90
Purchase #7	$160.27	4.527%	$167.5254	$167.53	$167.55	$167.50
7 purchase totals =	$791.37		$843.6788	$843.69	$843.70	$843.60