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	$241.71	5.659%	$255.3884	$255.39	$255.40	$255.40
Purchase #2	$50.38	6.242%	$53.5247	$53.52	$53.50	$53.50
Purchase #3	$106.31	4.597%	$111.1971	$111.20	$111.20	$111.20
Purchase #4	$168.46	6.446%	$179.3189	$179.32	$179.30	$179.30
Purchase #5	$128.91	11.252%	$143.415	$143.42	$143.40	$143.40
Purchase #6	$145.97	11.361%	$162.5537	$162.55	$162.55	$162.60
Purchase #7	$114.92	5.695%	$121.4647	$121.46	$121.45	$121.50
7 purchase totals =	$956.66		$1,026.8625	$1,026.86	$1,026.80	$1,026.90