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	$154.64	6.324%	$164.4194	$164.42	$164.40	$164.40
Purchase #2	$124.82	11.462%	$139.1269	$139.13	$139.15	$139.10
Purchase #3	$137.44	3.548%	$142.3164	$142.32	$142.30	$142.30
Purchase #4	$38.65	4.698%	$40.4658	$40.47	$40.45	$40.50
Purchase #5	$225.53	7.509%	$242.465	$242.47	$242.45	$242.50
Purchase #6	$136.43	10.530%	$150.7961	$150.80	$150.80	$150.80
Purchase #7	$211.99	10.690%	$234.6517	$234.65	$234.65	$234.70
7 purchase totals =	$1,029.50		$1,114.2413	$1,114.26	$1,114.20	$1,114.30