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	$135.58	5.783%	$143.4206	$143.42	$143.40	$143.40
Purchase #2	$59.43	9.505%	$65.0788	$65.08	$65.10	$65.10
Purchase #3	$151.55	12.581%	$170.6165	$170.62	$170.60	$170.60
Purchase #4	$194.72	12.749%	$219.5449	$219.54	$219.55	$219.50
Purchase #5	$50.53	10.672%	$55.9226	$55.92	$55.90	$55.90
Purchase #6	$224.28	11.673%	$250.4602	$250.46	$250.45	$250.50
Purchase #7	$171.47	5.748%	$181.3261	$181.33	$181.35	$181.30
7 purchase totals =	$987.56		$1,086.3697	$1,086.37	$1,086.35	$1,086.30