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	$171.72	7.632%	$184.8257	$184.83	$184.85	$184.80
Purchase #2	$182.83	12.182%	$205.1024	$205.10	$205.10	$205.10
Purchase #3	$11.83	5.491%	$12.4796	$12.48	$12.50	$12.50
Purchase #4	$58.68	9.667%	$64.3526	$64.35	$64.35	$64.40
Purchase #5	$158.80	7.731%	$171.0768	$171.08	$171.10	$171.10
Purchase #6	$109.61	12.750%	$123.5853	$123.59	$123.60	$123.60
Purchase #7	$228.63	3.192%	$235.9279	$235.93	$235.95	$235.90
7 purchase totals =	$922.10		$997.3503	$997.36	$997.45	$997.40