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	$55.74	10.186%	$61.4177	$61.42	$61.40	$61.40
Purchase #2	$141.62	7.348%	$152.0262	$152.03	$152.05	$152.00
Purchase #3	$233.87	9.275%	$255.5614	$255.56	$255.55	$255.60
Purchase #4	$38.62	12.250%	$43.351	$43.35	$43.35	$43.40
Purchase #5	$145.75	12.702%	$164.2632	$164.26	$164.25	$164.30
Purchase #6	$49.80	10.291%	$54.9249	$54.92	$54.90	$54.90
Purchase #7	$100.92	3.178%	$104.1272	$104.13	$104.15	$104.10
7 purchase totals =	$766.32		$835.6716	$835.67	$835.65	$835.70