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	$154.99	5.861%	$164.074	$164.07	$164.05	$164.10
Purchase #2	$60.35	10.779%	$66.8551	$66.86	$66.85	$66.90
Purchase #3	$36.89	8.145%	$39.8947	$39.89	$39.90	$39.90
Purchase #4	$40.46	7.698%	$43.5746	$43.57	$43.55	$43.60
Purchase #5	$113.25	10.545%	$125.1922	$125.19	$125.20	$125.20
Purchase #6	$23.62	13.728%	$26.8626	$26.86	$26.85	$26.90
Purchase #7	$89.27	12.205%	$100.1654	$100.17	$100.15	$100.20
7 purchase totals =	$518.83		$566.6186	$566.61	$566.55	$566.80