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	$143.37	9.488%	$156.9729	$156.97	$156.95	$157.00
Purchase #2	$167.96	7.266%	$180.164	$180.16	$180.15	$180.20
Purchase #3	$20.78	8.294%	$22.5035	$22.50	$22.50	$22.50
Purchase #4	$219.30	6.647%	$233.8769	$233.88	$233.90	$233.90
Purchase #5	$124.88	13.608%	$141.8737	$141.87	$141.85	$141.90
Purchase #6	$230.82	10.664%	$255.4346	$255.43	$255.45	$255.40
Purchase #7	$102.67	4.356%	$107.1423	$107.14	$107.15	$107.10
7 purchase totals =	$1,009.78		$1,097.9679	$1,097.95	$1,097.95	$1,098.00