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	$134.49	5.231%	$141.5252	$141.53	$141.55	$141.50
Purchase #2	$137.72	8.144%	$148.9359	$148.94	$148.95	$148.90
Purchase #3	$211.87	13.818%	$241.1462	$241.15	$241.15	$241.10
Purchase #4	$38.30	5.645%	$40.462	$40.46	$40.45	$40.50
Purchase #5	$11.42	9.332%	$12.4857	$12.49	$12.50	$12.50
Purchase #6	$164.70	6.598%	$175.5669	$175.57	$175.55	$175.60
Purchase #7	$227.35	10.475%	$251.1649	$251.16	$251.15	$251.20
7 purchase totals =	$925.85		$1,011.2868	$1,011.30	$1,011.30	$1,011.30