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	$146.48	9.484%	$160.3722	$160.37	$160.35	$160.40
Purchase #2	$245.44	10.612%	$271.4861	$271.49	$271.50	$271.50
Purchase #3	$244.80	5.859%	$259.1428	$259.14	$259.15	$259.10
Purchase #4	$141.44	6.664%	$150.8656	$150.87	$150.85	$150.90
Purchase #5	$158.54	11.200%	$176.2965	$176.30	$176.30	$176.30
Purchase #6	$154.90	6.242%	$164.5689	$164.57	$164.55	$164.60
Purchase #7	$153.72	5.665%	$162.4282	$162.43	$162.45	$162.40
7 purchase totals =	$1,245.32		$1,345.1603	$1,345.17	$1,345.15	$1,345.20