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	$205.33	11.706%	$229.3659	$229.37	$229.35	$229.40
Purchase #2	$250.30	3.299%	$258.5574	$258.56	$258.55	$258.60
Purchase #3	$50.37	13.145%	$56.9911	$56.99	$57.00	$57.00
Purchase #4	$126.39	12.838%	$142.6159	$142.62	$142.60	$142.60
Purchase #5	$199.25	6.382%	$211.9661	$211.97	$211.95	$212.00
Purchase #6	$118.58	3.777%	$123.0588	$123.06	$123.05	$123.10
Purchase #7	$57.34	12.281%	$64.3819	$64.38	$64.40	$64.40
7 purchase totals =	$1,007.56		$1,086.9371	$1,086.95	$1,086.90	$1,087.10