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	$117.34	13.153%	$132.7737	$132.77	$132.75	$132.80
Purchase #2	$173.53	4.797%	$181.8542	$181.85	$181.85	$181.90
Purchase #3	$155.33	6.136%	$164.861	$164.86	$164.85	$164.90
Purchase #4	$129.65	5.744%	$137.0971	$137.10	$137.10	$137.10
Purchase #5	$148.80	7.745%	$160.3246	$160.32	$160.30	$160.30
Purchase #6	$101.78	9.342%	$111.2883	$111.29	$111.30	$111.30
Purchase #7	$177.31	3.186%	$182.9591	$182.96	$182.95	$183.00
7 purchase totals =	$1,003.74		$1,071.1580	$1,071.15	$1,071.10	$1,071.30