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	$134.35	4.103%	$139.8624	$139.86	$139.85	$139.90
Purchase #2	$145.76	5.190%	$153.3249	$153.32	$153.30	$153.30
Purchase #3	$162.71	12.493%	$183.0374	$183.04	$183.05	$183.00
Purchase #4	$173.32	13.389%	$196.5258	$196.53	$196.55	$196.50
Purchase #5	$78.67	13.421%	$89.2283	$89.23	$89.25	$89.20
Purchase #6	$193.27	3.182%	$199.4199	$199.42	$199.40	$199.40
Purchase #7	$87.81	5.186%	$92.3638	$92.36	$92.35	$92.40
7 purchase totals =	$975.89		$1,053.7625	$1,053.76	$1,053.75	$1,053.70