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	$198.31	10.739%	$219.6065	$219.61	$219.60	$219.60
Purchase #2	$174.72	10.303%	$192.7214	$192.72	$192.70	$192.70
Purchase #3	$40.83	6.489%	$43.4795	$43.48	$43.50	$43.50
Purchase #4	$159.39	12.291%	$178.9806	$178.98	$179.00	$179.00
Purchase #5	$24.37	12.560%	$27.4309	$27.43	$27.45	$27.40
Purchase #6	$144.79	13.614%	$164.5017	$164.50	$164.50	$164.50
Purchase #7	$240.38	4.373%	$250.8918	$250.89	$250.90	$250.90
7 purchase totals =	$982.79		$1,077.6124	$1,077.61	$1,077.65	$1,077.60