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	$243.84	6.370%	$259.3726	$259.37	$259.35	$259.40
Purchase #2	$45.65	3.825%	$47.3961	$47.40	$47.40	$47.40
Purchase #3	$152.96	7.465%	$164.3785	$164.38	$164.40	$164.40
Purchase #4	$100.72	11.298%	$112.0993	$112.10	$112.10	$112.10
Purchase #5	$239.86	13.463%	$272.1524	$272.15	$272.15	$272.20
Purchase #6	$123.70	6.561%	$131.816	$131.82	$131.80	$131.80
Purchase #7	$20.85	5.324%	$21.9601	$21.96	$21.95	$22.00
7 purchase totals =	$927.58		$1,009.1750	$1,009.18	$1,009.15	$1,009.30