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	$111.31	11.344%	$123.937	$123.94	$123.95	$123.90
Purchase #2	$200.48	13.158%	$226.8592	$226.86	$226.85	$226.90
Purchase #3	$171.94	5.196%	$180.874	$180.87	$180.85	$180.90
Purchase #4	$167.29	9.224%	$182.7208	$182.72	$182.70	$182.70
Purchase #5	$115.58	13.362%	$131.0238	$131.02	$131.00	$131.00
Purchase #6	$180.83	13.823%	$205.8261	$205.83	$205.85	$205.80
Purchase #7	$59.77	9.548%	$65.4768	$65.48	$65.50	$65.50
7 purchase totals =	$1,007.20		$1,116.7177	$1,116.72	$1,116.70	$1,116.70