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	$109.76	9.275%	$119.9402	$119.94	$119.95	$119.90
Purchase #2	$105.45	3.611%	$109.2578	$109.26	$109.25	$109.30
Purchase #3	$49.98	3.202%	$51.5804	$51.58	$51.60	$51.60
Purchase #4	$208.55	6.172%	$221.4217	$221.42	$221.40	$221.40
Purchase #5	$147.42	5.199%	$155.0844	$155.08	$155.10	$155.10
Purchase #6	$223.96	3.462%	$231.7135	$231.71	$231.70	$231.70
Purchase #7	$36.69	13.285%	$41.5643	$41.56	$41.55	$41.60
7 purchase totals =	$881.81		$930.5623	$930.55	$930.55	$930.60