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	$242.40	5.394%	$255.4751	$255.48	$255.50	$255.50
Purchase #2	$213.98	5.617%	$225.9993	$226.00	$226.00	$226.00
Purchase #3	$104.78	7.119%	$112.2393	$112.24	$112.25	$112.20
Purchase #4	$197.81	10.422%	$218.4258	$218.43	$218.45	$218.40
Purchase #5	$162.56	10.161%	$179.0777	$179.08	$179.10	$179.10
Purchase #6	$109.69	6.527%	$116.8495	$116.85	$116.85	$116.80
Purchase #7	$52.79	12.722%	$59.5059	$59.51	$59.50	$59.50
7 purchase totals =	$1,084.01		$1,167.5726	$1,167.59	$1,167.65	$1,167.50