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	$42.61	3.726%	$44.1976	$44.20	$44.20	$44.20
Purchase #2	$6.39	4.293%	$6.6643	$6.66	$6.65	$6.70
Purchase #3	$201.59	10.257%	$222.2671	$222.27	$222.25	$222.30
Purchase #4	$43.28	5.455%	$45.6409	$45.64	$45.65	$45.60
Purchase #5	$209.52	6.842%	$223.8554	$223.86	$223.85	$223.90
Purchase #6	$52.59	5.853%	$55.6681	$55.67	$55.65	$55.70
Purchase #7	$241.71	6.368%	$257.1021	$257.10	$257.10	$257.10
7 purchase totals =	$797.69		$855.3955	$855.40	$855.35	$855.50