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	$44.44	6.636%	$47.389	$47.39	$47.40	$47.40
Purchase #2	$49.77	3.638%	$51.5806	$51.58	$51.60	$51.60
Purchase #3	$202.68	11.419%	$225.824	$225.82	$225.80	$225.80
Purchase #4	$207.52	8.738%	$225.6531	$225.65	$225.65	$225.70
Purchase #5	$191.96	3.218%	$198.1373	$198.14	$198.15	$198.10
Purchase #6	$101.81	3.447%	$105.3194	$105.32	$105.30	$105.30
Purchase #7	$136.65	4.333%	$142.571	$142.57	$142.55	$142.60
7 purchase totals =	$934.83		$996.4744	$996.47	$996.45	$996.50