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	$232.36	11.302%	$258.6213	$258.62	$258.60	$258.60
Purchase #2	$116.42	8.842%	$126.7139	$126.71	$126.70	$126.70
Purchase #3	$147.55	13.863%	$168.0049	$168.00	$168.00	$168.00
Purchase #4	$159.53	3.712%	$165.4518	$165.45	$165.45	$165.50
Purchase #5	$54.30	9.724%	$59.5801	$59.58	$59.60	$59.60
Purchase #6	$41.46	8.872%	$45.1383	$45.14	$45.15	$45.10
Purchase #7	$243.89	7.582%	$262.3817	$262.38	$262.40	$262.40
7 purchase totals =	$995.51		$1,085.8920	$1,085.88	$1,085.90	$1,085.90