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	$51.84	11.233%	$57.6632	$57.66	$57.65	$57.70
Purchase #2	$216.60	5.689%	$228.9224	$228.92	$228.90	$228.90
Purchase #3	$52.94	12.736%	$59.6824	$59.68	$59.70	$59.70
Purchase #4	$248.32	3.274%	$256.45	$256.45	$256.45	$256.50
Purchase #5	$225.26	4.612%	$235.649	$235.65	$235.65	$235.60
Purchase #6	$113.98	12.558%	$128.2936	$128.29	$128.30	$128.30
Purchase #7	$158.31	5.197%	$166.5374	$166.54	$166.55	$166.50
7 purchase totals =	$1,067.25		$1,133.1980	$1,133.19	$1,133.20	$1,133.20