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	$238.35	3.719%	$247.2142	$247.21	$247.20	$247.20
Purchase #2	$234.60	12.313%	$263.4863	$263.49	$263.50	$263.50
Purchase #3	$77.83	7.234%	$83.4602	$83.46	$83.45	$83.50
Purchase #4	$13.87	3.757%	$14.3911	$14.39	$14.40	$14.40
Purchase #5	$109.58	12.719%	$123.5175	$123.52	$123.50	$123.50
Purchase #6	$248.71	4.268%	$259.3249	$259.32	$259.30	$259.30
Purchase #7	$184.60	3.157%	$190.4278	$190.43	$190.45	$190.40
7 purchase totals =	$1,107.54		$1,181.8220	$1,181.82	$1,181.80	$1,181.80