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	$62.70	7.261%	$67.2526	$67.25	$67.25	$67.30
Purchase #2	$61.69	8.489%	$66.9269	$66.93	$66.95	$66.90
Purchase #3	$10.89	3.566%	$11.2783	$11.28	$11.30	$11.30
Purchase #4	$10.47	10.338%	$11.5524	$11.55	$11.55	$11.60
Purchase #5	$134.43	9.829%	$147.6431	$147.64	$147.65	$147.60
Purchase #6	$74.64	10.593%	$82.5466	$82.55	$82.55	$82.50
Purchase #7	$233.76	13.611%	$265.5771	$265.58	$265.60	$265.60
7 purchase totals =	$588.58		$652.7770	$652.78	$652.85	$652.80