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	$176.42	8.573%	$191.5445	$191.54	$191.55	$191.50
Purchase #2	$150.37	9.571%	$164.7619	$164.76	$164.75	$164.80
Purchase #3	$206.80	13.397%	$234.505	$234.51	$234.50	$234.50
Purchase #4	$160.53	3.749%	$166.5483	$166.55	$166.55	$166.50
Purchase #5	$241.56	6.167%	$256.457	$256.46	$256.45	$256.50
Purchase #6	$97.25	8.760%	$105.7691	$105.77	$105.75	$105.80
Purchase #7	$17.92	6.395%	$19.066	$19.07	$19.05	$19.10
7 purchase totals =	$1,050.85		$1,138.6518	$1,138.66	$1,138.60	$1,138.70