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	$49.93	9.265%	$54.556	$54.56	$54.55	$54.60
Purchase #2	$56.38	6.169%	$59.8581	$59.86	$59.85	$59.90
Purchase #3	$43.77	3.670%	$45.3764	$45.38	$45.40	$45.40
Purchase #4	$148.98	10.543%	$164.687	$164.69	$164.70	$164.70
Purchase #5	$60.91	13.719%	$69.2662	$69.27	$69.25	$69.30
Purchase #6	$87.28	3.638%	$90.4552	$90.46	$90.45	$90.50
Purchase #7	$232.80	3.580%	$241.1342	$241.13	$241.15	$241.10
7 purchase totals =	$680.05		$725.3331	$725.35	$725.35	$725.50