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	$46.71	4.836%	$48.9689	$48.97	$48.95	$49.00
Purchase #2	$172.94	4.383%	$180.52	$180.52	$180.50	$180.50
Purchase #3	$117.95	5.496%	$124.4325	$124.43	$124.45	$124.40
Purchase #4	$168.80	3.805%	$175.2228	$175.22	$175.20	$175.20
Purchase #5	$176.61	7.222%	$189.3648	$189.36	$189.35	$189.40
Purchase #6	$131.38	7.487%	$141.2164	$141.22	$141.20	$141.20
Purchase #7	$126.92	13.853%	$144.5022	$144.50	$144.50	$144.50
7 purchase totals =	$941.31		$1,004.2276	$1,004.22	$1,004.15	$1,004.20