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	$225.81	5.795%	$238.8957	$238.90	$238.90	$238.90
Purchase #2	$195.29	6.845%	$208.6576	$208.66	$208.65	$208.70
Purchase #3	$43.94	3.844%	$45.6291	$45.63	$45.65	$45.60
Purchase #4	$98.49	6.483%	$104.8751	$104.88	$104.90	$104.90
Purchase #5	$98.77	4.465%	$103.1801	$103.18	$103.20	$103.20
Purchase #6	$231.65	13.322%	$262.5104	$262.51	$262.50	$262.50
Purchase #7	$148.41	9.724%	$162.8414	$162.84	$162.85	$162.80
7 purchase totals =	$1,042.36		$1,126.5894	$1,126.60	$1,126.65	$1,126.60