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	$143.78	7.208%	$154.1437	$154.14	$154.15	$154.10
Purchase #2	$185.96	9.216%	$203.0981	$203.10	$203.10	$203.10
Purchase #3	$89.94	11.633%	$100.4027	$100.40	$100.40	$100.40
Purchase #4	$240.78	12.167%	$270.0757	$270.08	$270.10	$270.10
Purchase #5	$250.77	8.534%	$272.1707	$272.17	$272.15	$272.20
Purchase #6	$28.52	13.811%	$32.4589	$32.46	$32.45	$32.50
Purchase #7	$78.94	6.492%	$84.0648	$84.06	$84.05	$84.10
7 purchase totals =	$1,018.69		$1,116.4146	$1,116.41	$1,116.40	$1,116.50