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	$226.55	10.175%	$249.6015	$249.60	$249.60	$249.60
Purchase #2	$72.33	8.628%	$78.5706	$78.57	$78.55	$78.60
Purchase #3	$61.57	6.194%	$65.3836	$65.38	$65.40	$65.40
Purchase #4	$45.43	12.581%	$51.1455	$51.15	$51.15	$51.10
Purchase #5	$76.61	7.675%	$82.4898	$82.49	$82.50	$82.50
Purchase #6	$212.33	7.492%	$228.2378	$228.24	$228.25	$228.20
Purchase #7	$111.64	7.182%	$119.658	$119.66	$119.65	$119.70
7 purchase totals =	$806.46		$875.0868	$875.09	$875.10	$875.10