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	$224.60	9.700%	$246.3862	$246.39	$246.40	$246.40
Purchase #2	$142.95	7.604%	$153.8199	$153.82	$153.80	$153.80
Purchase #3	$116.53	13.528%	$132.2942	$132.29	$132.30	$132.30
Purchase #4	$47.38	10.585%	$52.3952	$52.40	$52.40	$52.40
Purchase #5	$143.89	4.852%	$150.8715	$150.87	$150.85	$150.90
Purchase #6	$91.39	10.582%	$101.0609	$101.06	$101.05	$101.10
Purchase #7	$159.61	12.686%	$179.8581	$179.86	$179.85	$179.90
7 purchase totals =	$926.35		$1,016.6860	$1,016.69	$1,016.65	$1,016.80