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	$156.93	9.474%	$171.7975	$171.80	$171.80	$171.80
Purchase #2	$99.39	12.534%	$111.8475	$111.85	$111.85	$111.80
Purchase #3	$146.46	4.622%	$153.2294	$153.23	$153.25	$153.20
Purchase #4	$41.65	3.260%	$43.0078	$43.01	$43.00	$43.00
Purchase #5	$161.49	5.131%	$169.7761	$169.78	$169.80	$169.80
Purchase #6	$144.81	12.146%	$162.3986	$162.40	$162.40	$162.40
Purchase #7	$197.25	5.469%	$208.0376	$208.04	$208.05	$208.00
7 purchase totals =	$947.98		$1,020.0945	$1,020.11	$1,020.15	$1,020.00