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	$201.35	3.526%	$208.4496	$208.45	$208.45	$208.40
Purchase #2	$174.35	10.831%	$193.2338	$193.23	$193.25	$193.20
Purchase #3	$40.71	11.776%	$45.504	$45.50	$45.50	$45.50
Purchase #4	$47.86	10.492%	$52.8815	$52.88	$52.90	$52.90
Purchase #5	$92.26	13.147%	$104.3894	$104.39	$104.40	$104.40
Purchase #6	$192.99	11.106%	$214.4235	$214.42	$214.40	$214.40
Purchase #7	$79.36	12.628%	$89.3816	$89.38	$89.40	$89.40
7 purchase totals =	$828.88		$908.2634	$908.25	$908.30	$908.20