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	$204.70	10.319%	$225.823	$225.82	$225.80	$225.80
Purchase #2	$98.60	3.672%	$102.2206	$102.22	$102.20	$102.20
Purchase #3	$17.81	9.750%	$19.5465	$19.55	$19.55	$19.50
Purchase #4	$228.42	12.333%	$256.591	$256.59	$256.60	$256.60
Purchase #5	$194.81	13.870%	$221.8301	$221.83	$221.85	$221.80
Purchase #6	$54.67	8.138%	$59.119	$59.12	$59.10	$59.10
Purchase #7	$219.69	9.833%	$241.2921	$241.29	$241.30	$241.30
7 purchase totals =	$1,018.70		$1,126.4223	$1,126.42	$1,126.40	$1,126.30