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	$115.65	10.228%	$127.4787	$127.48	$127.50	$127.50
Purchase #2	$60.91	10.504%	$67.308	$67.31	$67.30	$67.30
Purchase #3	$172.35	7.392%	$185.0901	$185.09	$185.10	$185.10
Purchase #4	$246.35	7.330%	$264.4075	$264.41	$264.40	$264.40
Purchase #5	$78.88	6.342%	$83.8826	$83.88	$83.90	$83.90
Purchase #6	$235.37	12.853%	$265.6221	$265.62	$265.60	$265.60
Purchase #7	$22.92	5.724%	$24.2319	$24.23	$24.25	$24.20
7 purchase totals =	$932.43		$1,018.0209	$1,018.02	$1,018.05	$1,018.00