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	$163.94	11.325%	$182.5062	$182.51	$182.50	$182.50
Purchase #2	$30.42	10.116%	$33.4973	$33.50	$33.50	$33.50
Purchase #3	$163.53	9.579%	$179.1945	$179.19	$179.20	$179.20
Purchase #4	$103.34	8.262%	$111.878	$111.88	$111.90	$111.90
Purchase #5	$85.31	4.434%	$89.0926	$89.09	$89.10	$89.10
Purchase #6	$110.47	7.553%	$118.8138	$118.81	$118.80	$118.80
Purchase #7	$105.44	4.409%	$110.0888	$110.09	$110.10	$110.10
7 purchase totals =	$762.45		$825.0712	$825.07	$825.10	$825.10