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	$102.83	8.196%	$111.2579	$111.26	$111.25	$111.30
Purchase #2	$83.33	7.439%	$89.5289	$89.53	$89.55	$89.50
Purchase #3	$163.57	8.581%	$177.6059	$177.61	$177.60	$177.60
Purchase #4	$215.85	6.373%	$229.6061	$229.61	$229.60	$229.60
Purchase #5	$221.37	8.339%	$239.83	$239.83	$239.85	$239.80
Purchase #6	$171.43	6.498%	$182.5695	$182.57	$182.55	$182.60
Purchase #7	$214.54	7.246%	$230.0856	$230.09	$230.10	$230.10
7 purchase totals =	$1,172.92		$1,260.4839	$1,260.50	$1,260.50	$1,260.50