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	$33.76	4.103%	$35.1452	$35.15	$35.15	$35.10
Purchase #2	$190.55	12.385%	$214.1496	$214.15	$214.15	$214.10
Purchase #3	$186.90	10.724%	$206.9432	$206.94	$206.95	$206.90
Purchase #4	$180.26	5.525%	$190.2194	$190.22	$190.20	$190.20
Purchase #5	$143.83	6.304%	$152.897	$152.90	$152.90	$152.90
Purchase #6	$92.94	6.606%	$99.0796	$99.08	$99.10	$99.10
Purchase #7	$163.57	11.238%	$181.952	$181.95	$181.95	$182.00
7 purchase totals =	$991.81		$1,080.3860	$1,080.39	$1,080.40	$1,080.30