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	$101.86	9.219%	$111.2505	$111.25	$111.25	$111.30
Purchase #2	$145.96	12.526%	$164.2429	$164.24	$164.25	$164.20
Purchase #3	$107.43	11.297%	$119.5664	$119.57	$119.55	$119.60
Purchase #4	$19.59	5.402%	$20.6483	$20.65	$20.65	$20.60
Purchase #5	$187.84	13.428%	$213.0632	$213.06	$213.05	$213.10
Purchase #6	$132.93	8.524%	$144.261	$144.26	$144.25	$144.30
Purchase #7	$217.94	4.453%	$227.6449	$227.64	$227.65	$227.60
7 purchase totals =	$913.55		$1,000.6772	$1,000.67	$1,000.65	$1,000.70