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	$131.89	9.212%	$144.0397	$144.04	$144.05	$144.00
Purchase #2	$108.91	13.167%	$123.2502	$123.25	$123.25	$123.30
Purchase #3	$95.29	8.528%	$103.4163	$103.42	$103.40	$103.40
Purchase #4	$38.29	5.651%	$40.4538	$40.45	$40.45	$40.50
Purchase #5	$223.72	12.637%	$251.9915	$251.99	$252.00	$252.00
Purchase #6	$98.80	7.837%	$106.543	$106.54	$106.55	$106.50
Purchase #7	$164.34	6.376%	$174.8183	$174.82	$174.80	$174.80
7 purchase totals =	$861.24		$944.5128	$944.51	$944.50	$944.50