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	$167.62	7.608%	$180.3725	$180.37	$180.35	$180.40
Purchase #2	$164.53	9.346%	$179.907	$179.91	$179.90	$179.90
Purchase #3	$79.32	12.765%	$89.4452	$89.45	$89.45	$89.40
Purchase #4	$77.89	5.533%	$82.1997	$82.20	$82.20	$82.20
Purchase #5	$13.43	13.355%	$15.2236	$15.22	$15.20	$15.20
Purchase #6	$108.55	4.192%	$113.1004	$113.10	$113.10	$113.10
Purchase #7	$136.65	3.688%	$141.6897	$141.69	$141.70	$141.70
7 purchase totals =	$747.99		$801.9381	$801.94	$801.90	$801.90